# [Wet Thumb Forum]-bba unstoppable?



## Southrock (Feb 3, 2003)

I've had a 180 gal tank set up for 3 years now, and it has been a continual fight against black beard algae. I live in the Chicago area, and even in the LFS's that have planted display tanks, there it is. About three months ago, I spent two ten-hour days cleaning, boiling, bleach dipping everything in the tank, and it only took about two weeks for this algae to rear its ugly head once again.
I would tear the whole tank down and rebuild it if I thought that would eliminate it, but I don't think it will. I've thought about removing the fish (cardinals) and use algeacide, but I'd rather not do that. If anyone knows that it would work, please let me know and I'd probably try it.
I would take everything out of the tank and run it dark for a month, too, but I've tried that about a year ago with no success.

Is this something everyone just lives with, or is there a way to eliminate it for good?

Sorry for the long post!

-SR


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## Southrock (Feb 3, 2003)

I've had a 180 gal tank set up for 3 years now, and it has been a continual fight against black beard algae. I live in the Chicago area, and even in the LFS's that have planted display tanks, there it is. About three months ago, I spent two ten-hour days cleaning, boiling, bleach dipping everything in the tank, and it only took about two weeks for this algae to rear its ugly head once again.
I would tear the whole tank down and rebuild it if I thought that would eliminate it, but I don't think it will. I've thought about removing the fish (cardinals) and use algeacide, but I'd rather not do that. If anyone knows that it would work, please let me know and I'd probably try it.
I would take everything out of the tank and run it dark for a month, too, but I've tried that about a year ago with no success.

Is this something everyone just lives with, or is there a way to eliminate it for good?

Sorry for the long post!

-SR


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## Roger Miller (Jun 19, 2004)

We don't all live with it, so there is a way to deal with it. If you can tell us more about your setup then we might be able to help. Pictures would help a lot. Let us know about your lighting, your plants, your fertilizer, whether or not you use CO2, your substrate and any other tidbits that come to mind.

Roger Miller

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_"The indispensible first step to getting the things you want out of life is this: Decide what you want" -- Ben Stein_


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## dennis (Mar 1, 2004)

Welcome Southrock. I have had a similar problem in the past wiht bba. I have found that a though cleaning hepls to rid it and slow it down but you can never really get rid of it until you tank is well balanced. Ferts, especially NO3, P and iron need to be fairly balanced with your lighing and CO2. My problem with the bba went away once I started with co2, nutrient dosing, 3 watts per gallon and good water circulation. I hear that sae and black mollies work but have no experience. Shrimp are all the rage right now and Rosy barbs seem to like the stuff as well, unfortunatly, algae eating teams only help, they cant remedy the problem. That are your tank specs? IU also suspect that if you lfs has it on their displays then I figure that is how you originally got it. That is how I got mine. Hope this helps some.

Dennis Dietz

http://webpages.charter.net/dennisdietz/Aquatic%20Endeavors.html


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## Southrock (Feb 3, 2003)

OK, here's what I've got going:
180 g tank with a heated laterite substrate, 6 96w pc lights, co2 injection (reactor), gh 8, kh 6, ph 6.8 - 7.0, I do weekly 50% water changes, bleach dipping some stem plants alternately about every 3 weeks (to remove bba), I add 5 tsp K2SO4, 2 tsp KNO3, 3/16 tsp PO4, 5 caps flourish. Then, every 2 days I add 1 1/2 tsp KNO3, 1/8 tsp PO4 and 5 caps of flourish.
I have an Eheim 2024 Pro going through the CO2 reactor, and a Magnum 300 going through a UV sterilyzer that I haven't had on for a couple of months now. I used to use it whenever I started getting green water, keeping it on for a couple days at most. It seems I've gotten the fert balance worked out as far as GW is concerned. I do notice some stem plants have a hard time at the shoot tips, while others grow like gangbusters. I suspected Calcium, but gh is OK. 
"?"
I'm kinda hoping it's not a lighting issue. The tank is 24" tall, I can't really fit any more PC lights in the hood.

I've had Rosey barbs, they didn't eat this stuff, but they did eat hair algae when it was a problem. SAEs didn't eat it either, though I had heard they would. I do still have 2 Bristlenose Plecs and 5 ottos that seem to take care of everything else.

Most plants grow great, bubbling and good color, until the bba starts taking hold.

Well, there you have it.
Thanks for your thoughts.

-SR


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## Candy (Dec 15, 2003)

I take it that bleaching everything wont get rid of bba? I recieved plants from someone and set them up in a new tank as quarentene. They had gotten very cold in shipping and I did not think bleaching them at the time was a great idea. The idea was to allow them to recover from the shipping then rip the tank down, bleaching everything (1/19 solution/2mins)before moving them to my main tank. The algae looks like scattered individual hairs, about 1/2 inch long and look litterally like beard hairs, very coarse looking. Some of these plants wont even tolerate bleach I suspect. Limnophilia I had planned to lime dip and put into a new container alone to see if it develops algae. So far it is the only plant of the group of plants that does not have this coarse hair like algae on the oldest growth. Now I am getting the impression that even bleach wont get rid of the spores


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## Planted Engineer (Jan 15, 2004)

Hi there,

Let me guess that PH=6.8 at night when there's more CO2 and PH=7.0 during day time? Anyway - a PH of 7 with K=6 means that during day time you have only 20 ppm CO2 with 3wpg. Not enough CO2 in my opinion.

Also please make sure that you have true SAEs, and if yes then expect them to avoid bba - not to eat an existing one.

I trust you determined the fertlization rate based on test kits? What I mean - you are sure you are not over fertilizing - aren't you?

PE.


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## Roger Miller (Jun 19, 2004)

3 years is a long time to be fighting one battle.

If lighting is a problem then it is a problem because there's too much of it, not too little. 576 watts of PC lighting is a lot of power to put over a 180 gallon tank. Common experience seems to be that larger tanks use light more efficiently; the watts per gallon necessary to grow any particular plant is lower in a large tank than in a small tank.

Your nutrient doses are very high. What do your test kits say are the concentrations of nitrate and phosphate? My 150 gallon tank is probably similar to yours (but a foot shorter I would guess) and I use a small fraction of the amount of fertilizer that you are adding. It's common these days to associate algae problems in high-light tanks with nutrient shortages. A shortage probably isn't your problem. I wonder if you might have stepped over some invisible high-light/high-nutrient line that most of us never get to.

Your CO2 levels fall into the range of 20-30 ppm and that should be fine.

If I were to pick one thing in your description that would really prolong your problem then it's your maintenance routine. Whenever you uproot a plant you set it back a little. Whenever you bleach a plant you damage the plant and slow its growth. Between those two effects you are probably promoting the algae by setting back your fastest growing plants.

Instead of bleaching the plants you should remove the beard algae by hand. Yes, I know it's tedious. You need to do that as frequently as you can -- at least do it while changing water; do it at least once during the week if you can. It could take three or four weeks for your plants to recover from the past bleach treatments so 3-4 weeks is the minimum time it's likely to take to fix the problem. While that is going on keep all the plant mass in the tank that you can. Only remove damaged and dying plant material.

A Magnum and an Eheim 2024 may not provide enough circulation for a 180 gallon tank.

A few more questions... What plants are you growing? Is it densely planted? Can you post pictures? That might save us a thousand words.

Roger Miller

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_"The indispensible first step to getting the things you want out of life is this: Decide what you want" -- Ben Stein_


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## Planted Engineer (Jan 15, 2004)

Roger,

U said



> quote:
> 
> Common experience seems to be that larger tanks use light more efficiently; the watts per gallon necessary to grow any particular plant is lower in a large tank than in a small tank


I know it's a common belief, Takashi Amano's 3 gallon tank has 30W while his giant tanks wpg is on the lowe side. But is there an explanation for that? Maybe you could point to a related research??

PE.


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## Rex Grigg (Jan 22, 2004)

How about this. The WPG rule is a rule of thumb. If you take a 1 watt bulb over 1 quart of water you have 4 wpg. But you won't be able to grow plants. Each plant needs a certain threshold of light energy to thrive. This is why smaller tanks need more light to reach that threshold. Now on larger tanks once you reach that threshold you are there. Take the standard 55 gallon tank and standard 75 gallon tank. The difference is the 75 gallon is just about 5" wider. Now, if you have 220 watts over a 55 gallon tank you have pretty much met most any plants light threshold. Take the same wattage over the 75 and instead of 4 wpg you have 2.93 wpg. But you have still met pretty much any plants threshold. In fact I would guess, even though I have never tried it, that you could grow every plant in the 75 that you could in the 55 equally well. Now take a standard 90 gallon. It's 4" taller than the 75 gallon. But with that same 220 watts which is only 2.4 wpg you can pretty much grow any plant in the 90 that you can in the 75, and perversely the 55 as well. Why? Because you have reached the minimum light threshold for almost all plants once you get to this point.

Why do we use the WPG rule? Because it pretty much works for common tank sizes and we really have nothing better. I have seen other formulas that claim to work better but when you use them they show you need something like 340 watts over a 55 gallon tank to get into the high light category. And on a 90 gallon tank they get into the range of something close to 600 watts. That's madness.










American by birth, Marine by the grace of God! This post spell checked with IESpell available at http://www.iespell.com

See my Profile for tank details.

See my planted tank FAQ at http://members.dsl-only.net/~rex/
Caution, contains content which will offend sensitive people. Rated PG 13


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## Roger Miller (Jun 19, 2004)

John Fritch and Erik Olson have both studied trends in light requirements by volume. John did his using data from Amano's books. Erik did his using Amano's data plus responses to a survey. Erik's article is at the krib and you can reach it and some follow-up discussion here:

http://www.thekrib.com/Plants/Tech/Lighting/

There are several reasons I can think of that explain the trend.

There is a huge difference when comparing very small tanks to larger tanks. The lights on many small tanks are actually held above the tank by several inches to more than a foot; a lot of the "nominal" light never even makes it into the little tank. The systems are remarkably inefficient.

For larger tanks, I think that with larger tanks more of the light gets used before it escapes through the sides. The amount of light -- proporationately speaking -- that escapes from a small tank is higher than the amount that escapes from a larger tank. One outcome of that is that larger tanks sometimes look dim compared to small tanks even if they have similar light densities.

Third and most easily demonstrated is that the larger lights used on bigger aquariums are generally more efficient than the smaller lights used on smaller aquariums. For instance, if you compare lumens/watt across the whole range of Sylvania's "C50" products you see that the 15 watt product delivers 35.9 lumens/watt and the 40 watt product delivers 47.3 lumens/watt.

There are other factors as well, like the relative ease of getting a good reflector on a big tank compared to a small tank. What it comes down to is as with most things larger systems are more efficient.

I think it's reasonable to question whether people with big tanks actually are growing the same plants as people with smaller tanks and more watts/gallon. The Senske's large display tanks for instance have low watts/gallon and they include some plants that other people grow in small tanks with much higher watts/gallon, but their tanks are often dominated by plants (swords and anubias, for instance) that don't have large light requirements. Really light-demanding plants (like glosso) are missing from their tanks.

In my case I know the trend holds true. When I move plants from my small tanks (3 watts/gallon) to my largest tank (2.2 watts/gallon) the plants respond with faster, more robust growth.

Roger Miller

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_"The indispensible first step to getting the things you want out of life is this: Decide what you want" -- Ben Stein_


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## Nebur (Aug 12, 2004)

I have a similar situation, brush algae grows on the plants, this weekend i tried something new, I armed myself with a toothbrush and clean every plant in the tank, now it looks a lot better, Yes, I destroyed some leaves but the tank looks a lot better now. 
I´m still looking for a way to get rid of the algae, any better ideas ?


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## Planted Engineer (Jan 15, 2004)

Hi,

I am aware of Erik's survery on the krib. This is how I decided to have 360W over my 190 gallon tank. But then, you know, one day after the launch of the tank I thought that I maybe light is not enough.... - it is then that I heard that 2 wpg is on the medium intensity side and even read somewhere that if the tank is tall (mine is 24") then more light escapes from the tank as you go deepr - it is just can't be reflected back because the angle is not sharp enough!! U can actually see the FLs if you get real closer to the substrate and look up to the FLs....

But on the other hand I grow glosso, and it's doing preety good and that's a suprise 

PE.


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## Roger Miller (Jun 19, 2004)

> quote:
> 
> Originally posted by Planted Engineer:
> I ... read somewhere that if the tank is tall (mine is 24") then more light escapes from the tank as you go deepr - it is just can't be reflected back because the angle is not sharp enough!! U can actually see the FLs if you get real closer to the substrate and look up to the FLs....


If I do that on my 24" deep tank I can see the lights. If I do it on my 10" deep tank I can see the lights.

Actually, someone mislead you. I had to go back to my optics book to make sure. More light is reflected back from the glass at the deeper parts of a tank then from the shallower. Here's a fairly academic exercise:








Consider an incident ray originating at a point and reaching the glass at different depths. The angle of incidence is the angle between the line normal to the glass and the incident ray. The angle of refraction is the angle between the line normal to the glass and the refracted ray. The angles of refraction at the water-glass and glass-water interfaces are determined by Snell's Law, which is shown at the bottom of the graphic. As it happens, the index of refraction  for the glass is insignificant because it falls out of the relationship.

If the ray is incident on the glass at a shallow depth then the angle of incidence is low and light passes through both sides of the glass. If the ray is incident on the glass at a deeper depth then the ray is refracted at the water/glass interface and completely reflected at the glass/air interface. The two different conditions are separated at the critical angle of incidence which would be 48.8 degrees.

Roger Miller

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_"The indispensible first step to getting the things you want out of life is this: Decide what you want" -- Ben Stein_


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## Southrock (Feb 3, 2003)

Wow - look what happens in just a day.
This turned into a pretty enlightening thread, didn't it!

About a year ago, I was dealing with the same issue and I only had 4 96w pc's, and a common response I heard was that on a 24" deep tank, 384 wpg was not enough. Just looking at the tank, it made sense to me - the lower growth seemed to be in much dimmer light, and that's where the bba would start. Even now, if one plant is shaded by another plant, or by driftwood, it is usually the first to become infested, although not by much.

Roger, I got the dosing measurements through a lot of Tom Barr reading. I used to measure NO3, PO4 and Iron using Hagen test kits, but I found them all to be pretty unreliable. Since science was my worst subject, and I can't seem to get my brain around the ppm - litre measurement scheme, I followed tom's advice on KNO3 and traces, and used Chuck Gadd's calculator for K2SO4. Granted, the K2SO4 dose is probably a little high, I've been doing that now for about 6 weeks. I'm reluctant to change it because "no more GW", but I also understand that might be the culprit in the withering shoot tip dilemma. As far as traces, I've been gradually upping the dose and watching the plants (and water), 5 caps seems to be the ceiling. I had been adding 2 caps of Iron (Flourish), until about 4 weeks ago. I suspected the Iron might be causing the shoot-tip problem.

Pictures are not a possibility - no digital camera. But, here are the plants that grow well (all eventually aquire bba):
Bacopa monnierri (Dwarf Bacopa)
Lysimachia nummularia (Creeping Penny)
Mayaca fluviatilis (!)
Ceratopteris cornuta (Watersprite)
Aponogeton ulvacious
Aponogeton undulatus
Aponogeton longiplumulosis

All of these crypts suffer moderately from bba:
willissi
lucens
balansae
wendtii

Plants that won't grow shoots:
Roatala macranda
Hygrophila corymbosa
Hygrophila difformis

There are also a couple of Madagascar lace plants that are being crippled to the point...-I'm just going to take them out.

I bleach the stem plants, remove leaves from the Apons and Crypts. Boil rocks, clean plumbing monthly. Scraping the leaves will prove very difficult - most times I'm on a 5' ladder in water up to my shoulder.

For most of the week, the plants look good, people are amazed when they see it, but I don't know how much longer I can fight the good fight.

Tell me to run it dark for three months.
Tell me to tear it down and start over.
Tell me to get rocks and cichlids. lol.
Tell me to use (gasp) algaecide!

All kidding aside, thanks for the help.

-SR


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## Roger Miller (Jun 19, 2004)

Southrock,

Could you describe your algae? You are using the abbreviation "bba" for "black beard algae" and I usually use the same abbreviation for "black brush algae." The two are different.

Beard algae is a grey filamentous algae that grows to form tangled beards that usually reach a couple inches in length and trail off from the edges of leaves.

Brush algae is a nearly black algae with short (usually < 1 cm), straight filaments that form tufts and matts on surfaces and can grow into solid carpets.

Which do you have?

Your description of the algae appearing on shaded plants makes sense for either algae as both of them seem to prosper best in shaded areas and under moderate to dim lighting.

As far as the dosing goes, you may have started with Tom's recommendations, but that isn't where you ended up. Your total potassium dose works out to 40 ppm/week; nitrate to 33 ppm/week; phosphate to 2.7 ppm/week (assuming potassium phosphate). Compare to Tom's recommendations of 20 ppm K (recently lowered); 5 or less ppm NO3; 1 or less of PO4. And I think some of Tom's recommendations are *high*!

Your Flourish dose is more than 3 times the maximum that Seachem recommends. It must cost a bundle.

Given 50% water changes these doses could accumulate as high as 80 ppm K, 66 ppm NO3 and 5.4 ppm PO4. The nitrate and phosphate aren't likely to accumulate that high, but potassium could come close. If the plants used all the nitrate you are providing ( about 7.5 ppm of N per week) then they would only need about 5 ppm of potassium per week for normal growth. That means that 87% of the potassium you dose is excess.

That potassium concentration is high, but with your hard water it probably should not be a problem. But for the nitrate and phosphate you really should be using test kits to understand your dosing and to try to regulate it a little.

Given your plant list from your last post I may be starting to understand your tank a little. It sounds like an ungainly combination of plants, lighting and fertilizer.

Your crypts are slow-growing plants with moderate to low requirements for both light and nutrients and a penchant to get what the need from the substrate. The aponogetons can be heavy feeders but they tend to be heavy *substrate* feeders. Moreover, the aponogetons when healthy can be very large; even in a 180 gallon tank they could shade much of the floor space. The ceratopterus can also get very large and -- especially if floating -- shade a large part of the space.

I'm impressed that you can get the Mayaca to grow well. Mine always gets eaten and stops growing. I'm not surprised that the Rotala macrandra isn't doing well; it is a picky plant. The hygrophila's should help you if you can get them growing, but they may not grow well if shaded.

If you let the plants shade a lot of the tank then it doesn't make that much difference whether or not your lighting is adequate or too bright. The shade will be unsuited for most fast-growing plants.

I think with those plants you probably should be dosing the water a *lot* less and maybe adding something to the substrate for root-feeding plants. The shaded areas should be good for many crypts but if you want to grow very many stem plants you will have to make sure they get good access to light. Anubias, dwarf sag and java ferns would be good additions for shaded areas.

And like I said, none of these plants are going to do very well when they are regularly uprooted and bleached.

Good luck with the tank.

Roger Miller

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_"The indispensible first step to getting the things you want out of life is this: Decide what you want" -- Ben Stein_


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## Southrock (Feb 3, 2003)

Thanks for the advice, Roger.

I had a much-too-long response explaining how I've come to these levels, but it got zapped into internet hell, and rather than re-type it all, let me try to bottom line my plan.

I'm going to reduce my ferts:
2 tsp K2SO4 - 8.9 ppm (based on 160 g of water)
1 tsp KNO3 - 5.67 ppm
.125 tsp KH2PO4 - .69 ppm
2.5 caps Flourish
All at water change.
KNO3, KH2PO4, and Flourish every 2 days.

Probably still a little high, but my past (untrusted) testing tells me nitrogen and phosphate disappear after a couple of days.

I'll stop bleaching, but here's my question - When I scrape the algae (brush algae) off of the leaves, is it then free-floating to land in a new home? Further, when plant mass becomes heavy, so will brush algae mass become heavy. How does it go away? Are you thinking that when plant growth accelerates, algae growth will decline? That's not what I'm thinking. I'm thinking the algae will consume plants if I leave it in there. How can I prevent that?

I'll try this for 6-8 weeks and see what happens.

Thanks for your help - its much appreciated.

-SR


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## EDGE (Feb 28, 2004)

You should hold back your dosage of po4 to almost 0. They are usually the culprit for bba. I did a total tear down to replace the faulty tank 1 1/2 week ago. As soon as I started feeding beefheart and added .14 ppm of po4 in the tank, the bba exploded.

I stopped dosing po4 to see if that will help with the bba problem, but continue to dose KNO3 and k2so4. They are always short in my tank.
I used a sera test kit and confirm that the NO3 in the tank only get boosted to the recommanded level from my dosage.

I have cut down to 2.5 ml of flourish/plantex dosage as well. They were causing a lot of hair algae in the tank at 5-10 ml dosage.

On a side note, the red flame sword just send out a new flower stalk today. I didn't think it would send out a flower stalk so quickly after trimming all the roots back to 3" long.

---------------------------
My 75 Gallon

A Canadian's Plant Traders website


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## imported_Zhima (Oct 9, 2003)

I don't know if this is true, but some people doing ponds use barley straw to get rid of bba. I heard it's the slow release of hydrogen peroxide that prohibits the algae growth.








Zhima


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## Anthon (Feb 26, 2004)

How much PO4 and NO3 have you got into your tank water ?

Versus BBA I wouldn't decrease PO4 ferts but only NO3. BBA loves high NO3O4 ratio but simply hate low ratio (the contrary is true for BGA).

_____________________________
Sorry for my bad english ...


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## aoebombcat (Jul 26, 2005)

I always used a small bag full (a hand full) of barley straw in my planted tank. It does help with BBA. Before I use Barley Straw, My tank was covered with all types of algeas, but since I have used it, I only see little spots here and there. I even starve my brushy nose pl*co to death w/out noticing it, found it bones weeks later.









But as far as I know it works.

Hope this helps

Sushi is good, only if it is not your fish.


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## EDGE (Feb 28, 2004)

I had a similar ratio as his new regime, and it was creating a mess of bba in the tank.

---------------------------
My 75 Gallon

A Canadian's Plant Traders website


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## Roger Miller (Jun 19, 2004)

> quote:
> 
> Originally posted by Southrock:
> 
> ...


You don't need the K2SO4 in the mix. If your water is up near 80 ppm of K now then it will take two 50% water changes without any new additions of K2SO4 or KNO3 just to get it down to 20 ppm.

An alternative to leaving the K2SO4 out completely would be to leave it out for a few weeks while the tank readjusts. Another alternative would be to do one or more large water changes now to reset the nutrient concentrations in your tank.



> quote:
> 
> I'll stop bleaching, but here's my question - When I scrape the algae (brush algae) off of the leaves, is it then free-floating to land in a new home?


I've never seen it reattach. You probably want to siphon the floating bits out of the tank.



> quote:
> 
> Further, when plant mass becomes heavy, so will brush algae mass become heavy. How does it go away? Are you thinking that when plant growth accelerates, algae growth will decline? That's not what I'm thinking. I'm thinking the algae will consume plants if I leave it in there. How can I prevent that?


It is common experience that when you change conditions and get healthy plant growth that algae growth declines. I don't think anyone actually understands the mechanism; no doubt it is not simple and it probably includes several different factors. Nutrient competition is *not* likely to be part of the picture.

I have a holding/nursery tank with crappy lighting, a tendency to get badly overgrown and (recently) a bad case of brush algae. I thinned the clutter to improve circulation and to get more light into the lower plants. There are no algae-eaters in the tank so I started removing the brush algae by hand. The leaves I cleaned stayed clean. I got such a burst of growth out of some of the plants (variegated Anubias nana and a chain sword) that I moved some of the excess into other tanks.

SAEs do eat brush algae. Their popularity is based on that fact. Unfortunately there are at least two other fish that are mistakenly sold as SAEs and the pretenders don't eat much algae at all.

Young chinese algae eaters will also eat brush algae, but only off from surfaces where their sucker mouths can get a grip. They won't clean the edges of leaves, for instance. Older CAEs aren't very good algae eaters; they suck slime and scales from other fish and can kill slow-moving tank mates. If you get CAEs then you probably want to get rid of them as soon as they start chasing other fish around.

As long as you are adding fertilizers you really do need to test for at least nitrate to help you manage conditions in your tank.



> quote:
> 
> I'll try this for 6-8 weeks and see what happens.


Good luck. Let us know how it works.

Roger Miller

------------
_"The indispensible first step to getting the things you want out of life is this: Decide what you want" -- Ben Stein_


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## Planted Engineer (Jan 15, 2004)

Roger,

Back to the light and depth discussion...

Here's the link to whoever told me about the total reflection thing - Actually it's Erik Olson:

http://fins.actwin.com/aquatic-plants/month.9510/msg00303.html

While I understand your logic - still 0-3 inches below the water surface - I don't see the FLs. As I go deepr - I can see first, second, third, fourth and finally fith fluorescent. Can't explain it.

Now if you are correct then it seems like most of the light does'nt escape from the tank once it gets there. But still - it doesn't escape on one hand but it probably doesn't reach the glosso on the other hand. It lights other plants... What I mean goes as follows. Suppose I have a 10 feet high tank - and please let's not talk about attenutations for now - and suppose that it's true that light doesn't escape and suppose that the only plant that I grow deep down there is glosso. My understanding is that it will grow like a weed. But now let's just add one tallll plant at the back of the tank and have the glosso as the front plant. In this case in order to shoot for the glosso I have to really aim - only fraction of the light is aimed at that direction. The rest of the light is 'stopped' at the back plant - see what I mean? Deeper tanks are problematic for front grass.

PE.


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## Roger Miller (Jun 19, 2004)

> quote:
> 
> Originally posted by Planted Engineer:
> Here's the link to whoever told me about the total reflection thing - Actually it's Erik Olson:


I suppose I can take that up with Erik at some other time.



> quote:
> 
> While I understand your logic - still 0-3 inches below the water surface - I don't see the FLs.


You can't see the flourescents because you can't see through the water surface. It isn't the front glass that's causing the problem.



> quote:
> 
> As I go deepr - I can see first, second, third, fourth and finally fith fluorescent. Can't explain it.


As I go deeper I see the back light first and the front light last, or with lights running front-to-back I see the back of the lights first.

No matter how low I go to look up at the lights, the image I see only comes through the top part of the glass.



> quote:
> 
> Now if you are correct then it seems like most of the light does'nt escape from the tank once it gets there.


 I didn't say that at all. The light escapes by refracting at the surface or by reflecting off from something in the tank and exiting through the glass at a sufficiently high angle.



> quote:
> 
> The rest of the light is 'stopped' at the back plant - see what I mean? Deeper tanks are problematic for front grass.


Interseption and shading are different problems entirely, and problems that you are free to avoid.

Roger Miller

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_"The indispensible first step to getting the things you want out of life is this: Decide what you want" -- Ben Stein_


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