algae problem: BGA bugging again and again in a relatively new tank


Prolific Poster
Feb 27, 2008
Holland / The Netherlands
Hi people,

I a little stressed out over here: the BGA (cyanobacteria) keeps coming back, no matter what I do (not assuming I did everything...) In the broad scale of FW aquaria, as owner I turning just on a few knobs…

The current setup is:
180x80x55, net 500 liters/130 US gallon. 2 x T5 49watt (Philips 830+840) for 16 hours at 100%, good aluminium reflectors. 1 eheim 2216 and 1 eheim 2218, with blue sponge and the white cotton wool. Eheim 2000 l/h (500gal/h) power head and a seperate setup with fluidized bed filter, Total gross current is 900 gal/h. CO2 diffusor and UVC 7 watt filter. 3-6mm gravel. CO2 is probe controlled at pH 6.7 with a KH of 7 degrees (maybe the double dropchecker I investigated yesterday is a better solution to keep my CO2 above 30ppm)

Dosing is:
every day 12ml/cc easylife carbo (to be sure, when CO2 can be too low due to mismeasuring)
3 days a week: 60ml KNO3 solution (50gr in 1000ml DW) = 18ppm/week KNO3 and 20ml KH2PO4 (10gr in 1000 DW) = 1.2ppm/week KH2PO4. In total 12 ppm/week NO3, 8 ppm/week K+, 0.8 ppm PO4.
3 days a week: 30ml CSM+B solution (25gr in 500ml DW) = 9ppm/week CSM+B.
After 50% water change on Sunday, I'm adding 20 gr patentkali (for 3 ppm magnesium and extra potassium) but planning to chang that to MgSO4 (Epsom salt?) which I got in stock.

In june I was finished building my new tank, started with to low biomass, no fastgrowing plants, 1 eheim 2216 which couldn't clean the water enough. But started with EI dosing due to succesfull results in a small tank. Plants were growing like mad, but also the algae. And BGA was taking over after introducing fish and feeding. I used a antibiotic which solved the problem of BGA but next my entire nitrifcation process was disturbed. I got an extra Eheim 2218 and powerhead for current and cleaning. Cleaning out filters is now done weekly. After a few weeks I’ve got green floating algae, green white mist/cloud, BBA and some other unidentified algae (other form of cyano?) were taking over. Installed a UVC 7 watt filter to get rid of the mist/cloud. After 2 weeks the water was clear again and a lot of algae were dying, introducing BGA (on plants and gravel, not the surface) again! I bought a lot, but mean a lot, real waterplants (Egeria densa) to boost O2 production (and other nice side effects) to establish a good water quality. I must say after two weeks now, BGA isn’t growing fast anymore, but isn’t retreating yet. I have decreased the intensity of light for 4 hours to 50%. Oh, and BBA is very well established in the tank also

Creating high biomass, a lot of real waterplants, good filter cleaning, dosing, good waterflow, CO2 + excel supported?

What other things can I do to win this thing besides the thing above?

Any hints/tips? (redo gravel, extreme gravel cleaning to eliminate anaerobe (rotting?) areas?