can't get rid of algae

FishFin23 · Post by **FishFin23** » 05 Jan 2005, 16:18

I have problems with brown and green algae in my 30 gallon cory tank. About 2 weeks ago, I took everything out except the gravel and soaked it in hot water and scrubbed brown and green algae off all the decorations. I replaced everything (including most of the water since there were no fish at the time), and now the algae is growing back. There are brown rust-like spots and a green film starting to grow on all the surfaces that receive light. Ammonia and nitrites are zero, and nitrates have stayed under 5ppm since I replaced everything. The filter is a Penguin bio-wheel 170, and has activated carbon and Seachem's Purigen (I thought this would help keep the nutrients under control). Temperature is 75-76 degrees, and I do a 25% water change every week. Right now there are only 3 bronze corys in the tank. I eventually plan on having about 11 or 12 corys in there. Are there any suggestions on how I can keep these two kinds of algae under control? Thanks in advance.

MatsP · Post by **MatsP** » 05 Jan 2005, 16:40

The brown algae problem will not be solved by this, but a suitable sized algae-eating pleco, such as a bristlenose or otocinclus should make swift work of most sorts of green algae.

There are two things that make algae growth:
1. Light.
2. Nutrients. This is mainly nitrates and phosphates.

If you remove one of those two, the algae should eventually disappear. Of course, this may have other side-effects that you don't want (i.e. no light -> fish tank looks boring, no nutrients -> no plants will grow). However, understanding what makes algae grow, makes it possible to understand how to improve on the situation.

Sunlight is "worse" than artificial light for making algae grow, so if you can avoid getting the tank hit by sunlight, you'll reduce the growth by some amount. This may of course involve moving the tank to some other place, which means emptying it, etc...

If you haven't got any plants in the tank, you may want to get some plants, because they will be able to compete with the algae for nutrients. It also creates some shade at the bottom of the tank, where algae will not grow.

The food you give the cory's will turn into nutrients for algae. If you're overfeeding, it will make things worse.

There are also chemicals that you can add to prevent the algae from growing, but I don't like this approach.

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Mats

FishFin23 · Post by **FishFin23** » 06 Jan 2005, 17:13

Thanks so much for the info MatsP! I think a lot of the algae may be due to how long I keep the lights on. A lot of times I'm not home to turn the lights off until late at night. I bought an inexpensive timer to keep the lights on for only 9 hours instead of the more than 12 the tank usually gets

. Hopefully that will work. If it doesn't then I guess I'll have to test the water for phosphates and look into the other suggestions you made. Would high levels of phosphate in tap water alone cause rampant algae growth?

MatsP · Post by **MatsP** » 07 Jan 2005, 10:02

A timer on the lights is a pretty good idea. I've got one for each of the three tanks we've got in the house at the moment. It also makes more "sense" to the fish to get a steady day/night rythm...

Phosphates can come from tap-water and from the food. But you don't HAVE to have high levels of phosphates to get algae growth, it's just that if the levels are high, it will make it grow quicker and more.

If most of the algae is green, try getting a algae-eating catfish, such as a Bristlenose (Ancistrus). It will clean things off... Just remember to feed it when the algae runs out. Zuchini/Courgette, Cucumber and similar are good foods, combined with algae wafers and a few bloodworms now and again. Get a male and a female and you'll have the joys of seeing babies too, most likely.

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Mats