# Recurring diatom algae issue in fishless plant growout tank



## Mjproost (Nov 17, 2005)

Hello all!

I have two fishless plant growout tanks and I haev the same issue in both. I can't seem to keep the diatom algae from continually returning. I would prefer not to put Ottos in because I would like not to have worry about killing them with high CO2 levels. 

Tank #1
20 long
130 watts 8800K PC
GH 5/KH 5
ph 6.2-6.4
NO3: 10-15
PO4: 2-3
TMG 7 mls every other day 
EI'ish fert scheme
weekly 50% WC

Tank #2
50 gallon(shorter 55) 
3- 4X OD 48" 6500K T8's
GH 5/KH 5
ph 6.6
NO3: 5-10
PO4: 1-2
TMG 10 mls every other day
EI'ish
Weekly 50% WC

I don't think the usual lack of light/excess nutrients is the issue. Unless the fact that neither have filtration of any kind could be an issue. They just have powerheads that I use to inject the CO2. 

What are some common methods for controlling this algae without Ottos?


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## MatPat (Mar 22, 2004)

Can you give us some more info about your tank? Diatom algae is common with newly set up tanks. How long has your tank been set up?

You list an "EI-ish" fertilizer routine for your tanks, could you be a bit more specific on how/when you add the ferts?

You 20g has around 6wpg. That may be a contributor to the algae depending on the answers to the above 2 questions. I assume the lights are arranged with one in the front and one in the back. Do they both come on at the same time and stay on for the same duration?

The 50g should have about 3wpg with ODNO lights. This should be a good range again, depending on your photoperiod and fertilization routine.

I have been using a powerhead only filtration set up on my 50g (48x18 footprint) for over 6 months now. It too is a fishless tank but I only have 80w of light on this tank since it is only 12" deep.

Your CO2 levels may be the problem. CO2 has been an issue for a lot of folks due to accurate measurement problems. You may want to take a sample of tank water and let it sit our for 24-48 hours and check the "rested" pH. It has been suggested that the difference between your "degassed" tank water and water straight from the tank should be a diference of 1 pH (i.e. 7.6 degassed and 6.6 tank) to achieve ~30ppm. You can find plenty of references to this method by doing a search.


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## Mjproost (Nov 17, 2005)

> Can you give us some more info about your tank? Diatom algae is common with newly set up tanks. How long has your tank been set up?


The 20 gallon 3 months
The 50 gallon 7 weeks



> You list an "EI-ish" fertilizer routine for your tanks, could you be a bit more specific on how/when you add the ferts?


Its hard to explain because I mix a solution of KNO3 and KH2PO4 seperately. It equates out to about the following doses every other day:
20 gallon lots of fast growing stems:
about 7/16 tsp KNO3
just under 1/8 tsp KH2PO4

50 gallon, some slower growing plants:
1/2 tsp KNO3
3/16 tsp KH2PO4



> Your CO2 levels may be the problem. CO2 has been an issue for a lot of folks due to accurate measurement problems. You may want to take a sample of tank water and let it sit our for 24-48 hours and check the "rested" pH. It has been suggested that the difference between your "degassed" tank water and water straight from the tank should be a diference of 1 pH (i.e. 7.6 degassed and 6.6 tank) to achieve ~30ppm. You can find plenty of references to this method by doing a search.


Yep, tried that. The 20 gallon goes down over 1.2 points, the 50 exactly 1.0.



> You 20g has around 6wpg. That may be a contributor to the algae depending on the answers to the above 2 questions. I assume the lights are arranged with one in the front and one in the back. Do they both come on at the same time and stay on for the same duration?
> 
> The 50g should have about 3wpg with ODNO lights. This should be a good range again, depending on your photoperiod and fertilization routine.


THe photo period on the 20 is 10 hours nad the 50 is 11. I have another 20 gallon, a 20 tall that has the same lighting and I have little no algae issues and never diatom algae. Actually, I was under the impression that low light levels were a contributor to diatom algae, not high light levels.



> I have been using a powerhead only filtration set up on my 50g (48x18 footprint) for over 6 months now. It too is a fishless tank but I only have 80w of light on this tank since it is only 12" deep.


Good to know that is not the issue.

UPDATE: the 20 is starting to develop some Green slime algae on the glass. I checked the tempa nd the tanks are getting into the 80's during the day. I have do something about that.


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## MatPat (Mar 22, 2004)

I recently had a green dust algae problem that was resolved in one tank by decreasing both the light intensity and duration. In another tank it was resolved by decreasing the light photoperiod alone. I now run all my tanks on an 8 hour photoperiod. This seems to greatly reduce the algae while still allowing the plants to grow. They do grow more slowly so this may not be a solution you are looking for. 

Since the tanks are fishless, I would increase the CO2 even more and see if that alleviates your algae issues. CO2 measurement has a lot to do with test kit accuracy. It is easy to be off on the CO2 by 10 or more ppm and when you are off, you are low more often than high. 

I would say your diatom algae will go away on its own since both tanks are fairly new. The green "slime" (A pic would be a great help) will need to be manually removed/cleaned, preferable before a water change. Turn off your filters before cleaning to keep it from being spread around the tank. Do your water change after to remove as much of the floating particles as possible.

Can you give a little more information on your solutions? Depending on how you mixed them you may not be adding enough with your dosing amounts. I too use separate solutions for dosing and mine are made to give me 0.5ppm of NO3 per ml and 0.2ppm of PO4 based on a 75g tank.


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## Mjproost (Nov 17, 2005)

> Can you give a little more information on your solutions?


My above calculations were off. I was just trying to simplify it becasue I use a gram scale and not teaspoons to make my solution. But, in the end as usual, I over complicated it.

Here is what I use to make my mix:

KNO3:
42 grams KNO3 in 300 ml water.
20 gallon 10 mls of above every other day.
50 gallon 20 mls every other day.

KH2PO4:
5.6 grams KH2PO4 in 300 ml water
20 gallon 10 mls every other day
50 gallon 20 mls every other day

I feel the tanks should be using more nutrients than they are.

Update on the green slime: I scraped it and did a water change and it seems not to be coming back.

Update on the diatom: It is coming back faster and faster, no mattter what I do. I think the problem might be dissolved organics or silicates. The things these two tanks have in common is the substrate and lack of filtration. It is different than any other tank I have done. I used unrinsed Soilmaster over a rather thick layer of coconut fiber. I am setting up a new 20 gallon with new substrate and would like to move the plants over to that tank.

Any experience with Potassium Permangenate treatment on L. Cuba, L. Pantal, L. Glandulosa, E. Setaceum(sp?), T. Manaus, and T. Belem. I am worried these plants will not react well to the treatment being they are already stressed from the algae. But, I don't want to move the diatoms over to the new tank either.What do you think?


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## MatPat (Mar 22, 2004)

Your solutions and dosing look pretty good though I would dose more PO4 if it were my tank 

Why did you use the coconut fiber under your Soilmaster? Most folks use peat moss and just a light dusting in a CO2 enriched tank. Maybe the coconut fiber is contributing to your algae issues. I used sphagnum peat (not sphagnum peat moss) in a tank one time and had some very bad BGA issues I suspect from the moss decomposing. I tore down the tank, gave it a good cleaning and sat it up again using using peat moss. No problems the second time around. 

If you have diatom algae on your plants, it should rub off very easily. If it doesn't, it's not diatoms.


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## Mjproost (Nov 17, 2005)

> Your solutions and dosing look pretty good though I would dose more PO4 if it were my tank


I was thinking of trying more PO4 next time. I will try that.



> Why did you use the coconut fiber under your Soilmaster? Most folks use peat moss and just a light dusting in a CO2 enriched tank. Maybe the coconut fiber is contributing to your algae issues.


Why? Because I had some around, my wife uses it for her crabs...err hermit crabs. I know many people who have used coconut fiber successfully, its supposed to be more stable, break down less easily than peat moss. I have used it before but a different brand. This stuff seems really dirty compared to the other stuff. I am going to try just a very fine dusting of fine peat moss this time.

What do you think about a mix of about 30% Schultz's and 70% Red Sea Flora Base in the 20 and the soilmaster unrinsed in the 50?

The Florabase has been taking up space in my basement for a while. One bag is not enough for a 20 gallon.


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## MatPat (Mar 22, 2004)

Mjproost said:


> I was thinking of trying more PO4 next time. I will try that.


Let us know how it works for you. I think you will be happy with the results 



Mjproost said:


> Why? Because I had some around, my wife uses it for her crabs...err hermit crabs. I know many people who have used coconut fiber successfully, its supposed to be more stable, break down less easily than peat moss. I have used it before but a different brand. This stuff seems really dirty compared to the other stuff. I am going to try just a very fine dusting of fine peat moss this time.


That's a good reason  I think that is how folks figured out how things work in the past. By trying new stuff we find out if it works or not. I've never used or even heard of folks using coconut fiber under their substrate.



Mjproost said:


> What do you think about a mix of about 30% Schultz's and 70% Red Sea Flora Base in the 20 and the soilmaster unrinsed in the 50?
> 
> The Florabase has been taking up space in my basement for a while. One bag is not enough for a 20 gallon.


I used a bag of Florabase, two bags of Schultz (20lbs) and a bag of Flourite in each of my 55g when I set them up for the same reason. The Florabase will eventually break down into a powder but I had good plant growth while these two tanks were set up. I also fertilized these tanks well so that probably contributed just as much to the growth.


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## Avalon (Mar 7, 2005)

I have a 10g fishless plant growout tank. When I started it, it had horrible diatom problems. I was only using a tiny power filter. When I upgraded to a Fluval 104, the problem seemed to get worse, along with some thread algae, and the green fuzzy stuff. The plants still grew, but algae was horrible. I cleaned the tank really well, dipping the plants in H202 for 30s. After replanting, the algae never came back. I still get a little diatom algae...or some brown slimy crap. I really don't know what it is, but it's easy to remove and isn't threatening the plants.

I use Florabase, and dose heavy ferts. It's not uncommon for me to have 40+ppm nitrates, and 3+ppm phosphates. Lots of TMG. 65w PC light. Lots of CO2. Temp 74-76. The key, I think lies in the plants and their happiness. When mine finally adjusted, they exploded with growth--about the time I cleaned the tank. I cleaned the tank because the plants needed to be pruned. I got rid of the algae, and the plants did the rest. Plants are L. "guinea," T. belem & manaus, L. "pantanal," & Nesaea "red."


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