Green hair alga

Rider · Jul 12, 2005

I have a cold water natural planted tank, about 55 gallons. The top level of the plants, down to about 2 inches below the surface, quickly gets swampled by some sort of alga that consists of long (1/2" to 2") fine hair-like strands. The lower level of the tank gets very little. I have tried more light (up to 140 Watts!) less light (down to 36 Watts), dosing nitrate up to 80 ppm, letting it drop to zero, 3 day black-outs, mechanical removal ...

It grows on some plants a lot more (Myriophyllum crispatum - completely covers the plant, eventually killing it by blocking out all light) than others (Potamogeton ochreatus growing vigorously, 3" per week, almost unaffected). It also grows in isolated patches on the glass.

It is the only variety of algae in the tank.

Any suggestions how I can get rid of this curse? I am not a natural plant zealot and I am quite happy to try fertilisers if that's what is needed.

trenac · Jul 13, 2005

First thing you need to do is be consistent with your dosing, lights, C02 etc., being inconsistent will cause more harm then good.

What we need to know is your water parameters...PH, KH, N03, P04 levels. This way we will be able to figure out what is causing your algae.

Do you inject C02?
How long has the tank been set up?

MatPat · Jul 13, 2005

The main cause of your algae, assuming you have NO3 and PO4 in the tank, is probably low CO2 levels.

When you raised/dropped your light levels, how long did you leave them at a set level before you changed them again?

As Trenac stated, you don't mention the use of CO2 or a fertilization schedule for your tank. Answering these questions would make it much easier for us to help you

Rider · Jul 13, 2005

More information on green hair alga

I don't use CO2 at all.

Because the plants are growing in a mixture of soil and compost, I went for three months without fertilising, during which time most of the plants grew very well, though never free of algae. I started off with too much light, but when I noticed that there was less algae in shaded areas, I reduced the light. Now most of the algae grows near the top, directly under the lamp (a single 4 foot fluorescent tube, 36 Watt, efficient reflector). Away from the lamp, and at greater depths, there is much less algae.

After reading somewhere that nitrate deficiency can encourage algae, I started dosing with potassium nitrate. This appeared to have the effect of reducing the (already low) amount of algae in the deeper parts of the tank - in fact some of this algae turned brown and died off. However the algae in the top two inches of the water continues to flourish.

Temperature about 17 deg C, pH about 8.

trenac · Jul 13, 2005

The current light you have setup (a single 4 foot fluorescent tube, 36 Watt, efficient reflector) is not enough for a 55G tank. I would run the 140 watts with pressurized C02, the C02 will help with the algae if keep at around 30ppm.

Besides above you need to get on a regular schedule of dosing ferts, micros & macros.

We still need to know your water parameters: N03, P04, KH.

Green hair alga

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