# [Wet Thumb Forum]-Persistent algae (Was Top soils - good or bad?)



## Rider (Mar 19, 2005)

Could it be that the discussion on "Top soils - good or bad? explains the algae problem I have in one of my tanks?

I have three low tech natural tanks. One is completely algae-free, low maintenance. One requires a clean-up every few weeks. 

The third is a nightmare. It is 4 foot, effective volume about 160 litres, unheated, not too many fish, heavily planted, mostly with various short, mat-forming plants and some Potamogeton crispus.

The problem tank has been going for about 8 months. It is utterly infested with long fine green filaments of algae that cover the plants and walls, plus a little brown beard algae. I have tried various anti-algae treatments, giving each method at least 4 weeks to see if it will be effective

* carbon in the filter: no effect
* floating Azolla: plant roots soon completely engulfed with algae and Azolla gradually dies and disappears within 2 weeks
* light varying from 1 Watt per gallon to 4 Watts per gallon: low light slowed the algae - slightly
* blackouts: algae back to normal within 4 days
* Simazine: killed most algae, but back to normal in 5 days
* dosing with nitrate (with or without phosphate): slight reduction
* vigorous aeration: slight reduction
* no circulation at all: no change
* keep direct light off soil at lower part of tank: no change
* frequent 50% water changes: slows growth noticeably for about 2 days.

I can see only one difference with the problem tank. All three tanks use the same garden soil that I dug out of my garden but the problem tank has, in addition, about 2 to 3 inches of commercial compost underneath the soil.

Could it be that the compost is leaching excess nutrients into the water column?

What do the experts here recommend?


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## Jane of Upton (Jul 28, 2005)

I think you answered your own question. I like your empirical approach though!

Yep, too much organic matter gets nutrients into the water column too fast to get used up by the plants. At only 8 months in with an "El Natural" setup, this is still a relatively "young" tank. 

How about some floating plants with more robust root systems than azolla? Water lettuce (if you can fit it in the tank, open-topped is best) has a huge root system. Other plants that are good when using a glass canopy (ie, they "fit" in the space allowed) are Salvinia auriculata and Frogbit. Personally, I actually think that Salvinia has an inhibitory effect on green hair algae (alleopathic chemistry). I introduced some to a tank I run which had a slight, but on-again, off-again problem with stringy green fillamentous algae, and within a few weeks, there was no more to be found. Interestingly, the fillamentous algae tried to make a comeback shortly after a partial water change, which leads me to believe there was something inhibiting it in the water (from the salvinia) which I diluted when doing the water change. I've always kept at least a bit of salvinia in that tank ever since, as a preventative measure. 

Floating plants will compete very effectively with the algae. The bigger the root system, the better. If you have a bit of surface flow to keep them moving around the surface, they won't "shade" a certain spot all day.

Also, do you have any algae-eating critters? Algae eating fish, Shrimp, or Snails? These can be a big help as well.

Hope this helps.
-Jane


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## Endlersmom (Feb 29, 2004)

Rider,

Sorry to hear about the problems.

I can not say if it is the compost.

I planted 3 tanks just over 3 months ago. They went through various algae stages etc.

The large tank 5 feet, still has not cleared up. Green Water. Short algae along gravel(I can live with.)

All 3 have the same soils underlay.

Is it that the bigger tanks longer to stabilize, lightbulb issues, sunlight issues on and on.

I wish you luck.


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## Miss Fishy (May 13, 2006)

Rider, did you try the things on your list all at once or one at a time? If you tried them all separately, as is implied, then perhaps that is why none of them had much of an effect. In her book, Diana recommends _simultaneously_ putting carbon in the filter, adding extra floating plants, keeping direct light off the soil layer, reducing light and removing the algae by hand.

As I understand it, the best algae control is to have vigorously growing plants. Diana's suggestions are designed to disadvantage algae while at the same time helping the plants get the upper hand. Some of the things you tried (e.g. frequent water changes and blackouts) seem to me likely to weaken your plants and deprive them of nutrients, rather than helping them compete with the algae.

How is the overall plant growth in your tank? How often do you have to prune? If I remember correctly, you have _Triglochin_ sp., _Vallisneria_ sp., _Crassula helmsii_, _Myriophyllum_ sp., _Marsilea_ sp. and _Lilaeopsis_ sp. in this tank as well as the _Potamogeton crispus_. Some of these plants are pretty fast growers so if you can get them going I would think they would be good at keeping the algae in check.

I agree you need floating plants! Do not try Salvinia 'though - it is classified as a noxious weed here and you could get a hefty fine.

If you have 2 - 3 inches of compost under the soil and gravel layers, the depth of your substrate must be about 6 or 7 inches! What with the compost and all, no wonder you are having algae problems!

Good luck, and stick with it! As Jane and Endlersmom said, 8 months isn't very long in low-tech terms, even without the compost.

From Alex.


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## Rider (Mar 19, 2005)

Hi Alex

Yes, I tried the approach from Diana's book, to the letter of the law. It didn't help much.

Most of the vascular plants are doing well: P. crispus sending runners in all directins and pearling madly, Lilaeopsis and Marsilea spreading happily. The Triglochin gradually disintegrated, but I have since learned that this is difficult to grow anyway. The Myriophyllum and Crassula are struggling, because they are coated in algae. It is interesting to note that the Lilaeopsis seems to be algae-repellent - it has less algae on it than the glass!

Reading between the lines, are you also of the opinion that the algae is flourishing because the compost is putting nutrients into the water?


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## imported_BobB (Feb 26, 2005)

Rider-Do you know your iron levels in the various tanks?
Also. it's been my experience that no two tanks are the same....even if you set them up identically. That makes accurate diagnosis even more difficult.


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## Rider (Mar 19, 2005)

G'day BobB

No, I don't know the iron levels. Can you recomend a test kit to measure it? More importantly, suppose the iron level was too high, how would I get it down?

Thanks for the tip.


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## dwalstad (Apr 14, 2006)

> I can see only one difference with the problem tank. All three tanks use the same garden soil that I dug out of my garden but the problem tank has, in addition, about 2 to 3 inches of commercial compost underneath the soil.


Dear Rider,

Two to three inches of compost under a soil layer? Wow!

This tank is ideal for water lilies and emergent plants. There's no way submerged plants and small floating plants (alone) can handle this heavy nutrient load. They're going to need lots of help.

Compost is organic matter that will decompose into nutrients. It will also produce chelators that solubilize iron and other metals in the soil layer. Your tank is "bathed in nutrients".

I would add Water Sprite, Red Tiger Lotus, and other emergent, strongly rooted plants. Remember that emergent plants require decent lighting.

Folks, this is why I recommend a 1-1.5 inch layer of _unfertilized_ soil. A dab of compost probably won't hurt, but 2-3 inches of compost under the soil? Bring in the watersprite and water lilies!

Rider, thanks for your post and careful observations. Very helpful!


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## Rider (Mar 19, 2005)

I have since seen an astonishing turnaround. I did a 30% water change, went away for a week, (leaving someone to feed the fish of course) came home and found the tank infested with the heaviest growth of algae yet. Sigh... Did a 30% water change on two successive days. Then I noticed something odd. The algae was diminishing quickly. Over a period of a week, the Eleocharis grass and the Potamogeton burst into explosive growth and the green algae disappeared. I waited two weeks befroe posting this, because it seemed too good to be true.

So what is going on? I honestly don't know, but here is a guess. The tank is unheated, but we have had some warm weather here (summer in Australia - a few days in the high 30s/low40s Centigrade). Maybe the warm temperature triggered growth in the Eleocharis. Now, I have noticed that this grass never got tufts of algae attached to it, even when everything else in the tank was overrun. Allelopathy anyone?


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## dwalstad (Apr 14, 2006)

Temperature changes can certainly affect plant growth. Sounds like the plants got what they needed.

Strong evidence for allelopathy (root-released inhibitors) was made for one Eleocharis species (p. 45 my book).

Aren't ecosystems great?


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## Jane of Upton (Jul 28, 2005)

Wow, Rider, that IS one heck of a turnaround!

This also just made me think of a possible reason why a watersprite in my 20H won't stay rooted. This thing was fine, with a nice large root system (I'd bump into it planting its babies at its feet) until a few months after adding Giant Hairgrass in the back next to it. Now this big "mama plant" keeps uprooting itself - the root system is surprisingly small, and I keep replanting it, only to find it tumbling around the tank a few days later. I wonder if its the hairgrass roots?

Anyhow, this is great news that the other plants have finally gotten the upper hand! I would think the Potamogeton would be OK with lower temps, as it is a "pond plant" in several non-southern states around here. Perhaps it just finally reached critical mass in terms of established roots, etc. 

Thanks for posting the update!
-Jane


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## Miss Fishy (May 13, 2006)

I'm glad your tank is algae-free at last, Rider! 

Every summer I also see a huge increase in growth rates in my tanks (all unheated) and ponds. This is the time of year when those persistent algae problems just disappear overnight! Even my ponds with "coldwater" plants that grow all year round sometimes get overrun with algae during winter when their growth is slower, especially if the pond isn't very old. 

From Alex.


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