BGA in low-tech discus tank


Junior Poster
Jan 24, 2005
My tank is 220 lt. with 4 adult discus and quite heavyly planted: crypto + some swords + vallisneria. I have no co2 and I do not dose any fertilizer but light is quite over-powered: metal halide 150 W (8 h per day).
The tank is running for 2 years with no major algae problems.
Recently I experienced some BGA issues.
Could it be that NO3 level is too low? I actually have around 10-15 mg/lt. Despite the fish are very well feeded everyday, the NO3 level is maintained quite low because of the slow filter and floating plants.
In the next days I’ll downgrade my lamp to 70 W and probably prolongue photoperiod to 10 hours.
What else should I do to get rid of BBA? Should I add KNO3 as it seems according to most recent theories? I’ve been always told that in a discus tank the lower NO3 the better it is... It’s a kind of sacrilege for me to add NO3 artificially... :eek:

Thanks for support!


Guru Class Expert
Feb 3, 2005
Rochester, NH
Re: BGA in low-tech discus tank

How bad is the BGA?

BGA is caused by low nitrates or poor maintenance. Don't necessarily believe your test kit. Reducing the lighting and prolonging the photoperiod will not get rid of it. Bear with me if you already know some of this. :D

BGA is an algae/bacteria. The best ways to kill it are a total blackout of 3 days, or antibiotics (which you need to be very careful with). The fish and plants will be fine for three days with no light. I have had to do this twice myself.

At any rate, you need to correct what is causing it in the first place as well. You need to dose KNO3. I believe I read somewhere on this site that somebody has kept discus with high nitrate levels just fine (I have no experience to offer you here).

If you use Jobe's plant spikes, you will need to remove those as well.

Hope this helps