About to give up. Endless algae after adding PC fixture.

[Logan Zoo]

We set up a new 65 gal. planted tank in January. We have a trouble free 75 gal. tank that we harvest enough plants from to use in the new tank and give away. It is a fully stocked community tank with a 4' shop light. For the new tank I started with a 4-5" layer of ecco complete, a large cannister filter and a 4' shop light which hung over both ends of the tank. The tank prospered and we had to give away a lot of plants. I saved for a good light and in May installed an AH Supply 96 watt PC fixture. Within days I had an algae bloom. I have varied the hours that the light is on and can not get rid of the algae. It is a thick heavy dark green blanked that can be picked up with your fingers. It clogs the filter inlet in 24 hours and coats the plants. We have replanted 3 times. Water tests are PH 7.0, Phosphate .75 ppm, KH 35.8 PPM, GH 17.9 ppm, Nitrate 0, Ammonia 0, temp. 84 degrees. Current residents 1 Discus 1 lrg. Albino Red Tailed Shark, 3 Clown Loaches and 4 Neon Tetras. Unless you have any suggestions I am ready to sell this light and go back to my shop light. I do weekly 40% water changes.

Thanks.

Kevin

 

[tetrin]

the problem lies with your nitrates. you have to bump it up to get rid of the cyanobacteria. i use dry KNO3.

 

[malkore]

0ppm nitrate is your problem.

you have no nitrates, and cyanobacteria has taken hold in the tank. my guess is it forms sheets that are somewhat fragile, and when removed from the tank, it has a rather strong odor (like sickly sweet freshly cut grass).

you only have about 1.5watts per gallon, so bump your nitrate up to 10ppm using potassium nitrate (KNO3, available from www.gregwatson.com very cheaply)

get the nitrates up, and consider a 5 day complete black out (wrap the tank with layers of newspaper, or a towel..something...let no light in)

Worst case scenario, if the blackout does not work, remove as much as possible manually, then treat the tank with Maracyn, use a full dose on day one, then a half dose every day for another 5-6 days. the cyano will be gone after that.

The increased light from the PC bulb caused plants to soak up all nitrate, and your low fish load no longer provides enough natural nitrate to keep 10ppm. cyano is actually a bacteria (some 1,000 various species) and they show up when current is too low, or when nitrates hit zero.

Good luck!