Slime Algae Problem

[Duncan]

Hi Everyone,

I've been fighting a slime algae/cyanobacteria bloom in my 66 gallon Lake Tanganyika/Rainbowfish Tank for about the last 3-4 months. It came out of the blue and doesn't want to leave! If you are not familiar with this type of algae, think "thin, dark green jello" that smothers all available surfaces, including plants, rocks, gravel and glass. Thankfully not the fish!

The tank parameters are all "normal," slightly alkaline pH, negligeable nitrate, no ammonia, and up until recently, regular water changes (every 10 days -2 weeks) etc. I don't have a phosphate test kit, so I guess that's a possibilty, but any other suggestions? I've had these types of blooms in the past, but usually have been able to eradicate them by upping water changes (right now I've been going about a 40% change every 5-7 days).

There is only a single 40W "Lifeglow" tube above, as the plants in it are all low light, including a huge mass of java fern and a little bit of Anubias. I don't like to use erythromycin (I've heard this will work to treat these blooms), but am almost at the point of trying anything. Let me know what you may have tried and if you can see a problem I might have missed. This tank is right next to my 54 gallon planted tank from an earlier thread so its not like I have this problem in all my tanks, just this one! Aarggh!

Thanks for your help,
Duncan