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Green mat-algae experience - my 5 cts and some questions

3792 Views 5 Replies 5 Participants Last post by  jargonchipmunk
Hi all,

My aquarium has been installed around the end of august, the natural way of course.

From the beginning I have had quite good plant growth, however, after about 8 weeks green-mat algae started to develop.

I have implemented all of Diana's advice on how to fight the algae but nothing seems to work.

My Nitrates are 0, my Phosphorus is around 0,25 which is also not too high.

After a while I have started to implement Co2 the natural way (yeast and sugared water).

No change in plant growth, no change in algae. I still continue doing this, since this is the most natural way to keep my PH around 7.0. Even though I have added the Co2, my plants do look quite nice and colorfull but they do not grow that fast that I have to do some pruning every week like other people seem to need doing.

I have started experimenting a little with Nitrates and Phosporus ratios (Redfield Ratio) and have added some KnO3. Result: Nitrates got sky high and green algae started to grow more lushious than ever before. As you might know there is a theory stating that good plant growth seems to be dependent on the ration between N and P in the tank and in all natural waters for that matter (?!?).

I stopped it immediately. Luckily the Pistia Stratiotes took care of the Nitrates within a week; they are back to zero.

Since Diana suggests that there is a link between iron availability and algal growth, I have tested the iron values several times, but there is no iron to be found in my tank, at least not in the water.

Than I started thinking! Typical spots for the algae to develop are the bottom part between the Echnidorus Tenellus and in the top part between the roots of the Pistia.

Since the outlet of my pump is situated in the upper part of the tank, making the water drip from a level glass strip into the tank, there is not much circulation between the plants and dirt (POC) gathers especially in afore mentioned spots.

I started assuming that there might be quite some difference in measurements of Nitrate and Phosphorus values depending on where I took the testing water from the tank. Indeed there is quite a difference between bottom values and surface values. Especially phosphorus values vary at least 0,10 ppm or more (I will run some more tests coming up weeks and keep you posted).

As I started sucking up algae from the bottom part it struck me how dirty this part has become and I feel that there must be some connection between the dirt (POC Diana would call it) and the growing of green-mat algae.

So, I have adjusted the outlet and I seem to see a little improvement in the situation although I am not convinced that I have found the solution.

My questions now are:

1. Should I reduce the number of fish in my tank? I have a tank measuring 130 x 40 x 40 cm and my population consists of: 10 Tiger barbs, 9 Sherry barbs, 6 Ottocinclus Vittattus, 2 Trichogaster Leeri, and 3 Epiplatys Bardoi?

2. In spite of Diana stating that it is OK to leave the POC inside the tank, should I not try to keep it as clean as possible to see if it influences algal growth? Or should I perhaps increase circulation? My pump does some 300 liters an hour so the tank water is being revolved more than once an hour this way.

3. What do you all think about the Redfield Ratio? Anyone experimented that way?

Well, these are my questions right now.

I would love to make the algae disappear and do not feel very happy that my natural tanks does not seem to behave properly.

Looking forward to receiving your answers (perhaps even Diana's answers ?!?)


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Hello Frank,

Sounds like its time to clean the tank. :)

The POC accumulation indicates that the tank water isn't being oxygenated sufficiently. There's not enough oxygen for bacteria to decompose organic matter into plant nutrients. If a lot of POC accumulates on substrate, the underlying soil could become severely anaerobic, kill plants, and cause a tank meltdown.

I would remove some of the POC and increase water circulation. Water should circulate enough so that the top water layer and bottom water layer are more homogeneous. If you have an air pump, you could run a hose to the uncirculated part of the tank.

While I've cautioned against excessive water circulation and oxygenation, moderate water movement actually helps plants (my book, p. 104). It will provide oxygen to bacteria that decompose organic matter into CO2 and plant nutrients for plants. It will bring nutrients to plant leaves faster.

Your fish load is probably fine IF plants are growing well and water is sufficiently oxygenated.

I would stop the artificial CO2 injection, especially when oxygen may be a problem. Your fish could be in danger. Also, you're just going to induce nutrient deficiencies in your plants with the CO2 injection.
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What are the lighting arrangement in your tank?
Plants need light, Co2 and nutrients, all three to grow, when any of these three is out of balance, plant growth suffers and algae takes over.
Putting in co2 & nutrients will again create an imbalance in your aquariums and algae will not go away.
just my 2 cents.
By green mat algae do you mean blue green algae (BGA)?

There's lots of good algae id guides on the web such as this one

I had nasty outbrake of BGA a few years ago long before I moved over to the El natural style of planting and the BGA seemed to start on the roots of Pistia Stratiotes. I got over the BGA problem by removing the Pistia Stratiotes from my tank. A shame really as it is an attractive floating plant.

I also had a the beginnings of a BGA outbreak with my El natural set up but this time I had riccia as my floating plant and again the problem seemed to go away by removing most of the riccia.

In both cases I had a fairly densly planted tank and I wonder if the rampant growth of the floating plants plus the submerged plants stripped the tank of nitrates which in turn caused the BGA.

If I were to keep pistia now I would keep its growth under control - only a few plantlets.
What are the lighting arrangement in your tank?
Plants need light, Co2 and nutrients, all three to grow, when any of these three is out of balance, plant growth suffers and algae takes over.
Putting in co2 & nutrients will again create an imbalance in your aquariums and algae will not go away.
just my 2 cents.
Hi Sandree,

I have a lot of light above the tank. I am using T5 lights and I have 4 pieces of 54Watts each.
The colors are: 860 and 320

I did stop the CO2 meanwhile and I am trying to improve the waterflow in my tank. I'll keep yu guys posted. I am sorry it takes some times since I am pretty busy being a teacher.

All the best and Thx for answering all of you.
if I'm reading this right, that's quite a lot of light for an El Naturale setup!

the one suggestion aside from addressing the possibility of too much light for the slow grow setup, would be to look into the circulation issue. BGA is fought off best with good flow, and as Diana pointed out, you need that flow to oxygenate the lower levels to properly keep your bacteria colonies healthy so they can break down the waste matter into good plantfood :)
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