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Can low light cause BBA?


5 Sep 2017
Leicester. UK
For the last 2 years or so I have been fighting a battle with BBA! I've tried bleach and H202 to no avail.
Yesterday I tried again, soaked my rocks in a bleach-water mix, pulled my plants to bits, getting rid of all those ugly
black leaves, cleaned the filter, etc.

Gave up on Co2, but hope to try again, some say not enough Co2 can cause BBA too!

But last night after the wife had gone to bed and switched the room light off, and I switched the TV off, in the complete darkness,
I noticed a glow from the tank, a RIO180-LED. The tank lights go off at 10pm, it was now about 11.30pm has the water
level was lower then normal, I could see the LEDS dimly glowing.

This tank has a digital timer which perhaps uses a Triac as an electronic switch, but perhaps a small leakage current
is still driving the LEDS as they need little current to just glow.

I don't know that much about algae, but I'm sure I read that some types will live and flourish well in consistant very low
light levels. Could this be the problem? I'm today going to change to a mechanical timer from another tank, and check how
that works. My RIO125 uses the same timer, but this is an older RIO with T5 lighting and so no problem!

Lights are on 9-10am & 5-10pm, is 6 hours ment to be about right?
This morning the BBA is looking very GRAY! as I have returned my rocks, wood and plants to the tank.

Any comments please, more later...



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14 Mar 2018
The answer depends on how you define low light.

Light below the threshold to support low light plants will not trigger bba, but any light above the threshold but below intense light will. I had not encountered bba in my fish only tanks with light bright enough for viewing, but as soon as I raised the light bright enough to grow Java fern and Anubias, bba popped up I had to deal with. On the other extreme, I have planted bowls by the window that receive afternoon sunlight, I have never encountered bba but other green algae though. In fact, when I placed bba infested plants into the bowles, the bba disappeared within days, possibly out competed by green algae.

bba is red algae which thrive in lower light spectrum than green and brown algae. Apparently, bba thrive best in low to medium light but not in intense high light above certain threshold. Based on measurements of my setups, my estimates of the lower and upper thresholds are, repectively, 20 and 200 PAR.


1 Jan 2016
From my experience, BBA is caused by a build up of organics first and can also be triggered by high nitrates and high lights. High lights and low/fluctuating CO2 is not a good idea unless you have really easy fast growing plants and a clean tank.
Keeping the tank and filter clean is the no1 thing to do. I would also cover one of your LED bulbs(black electrical tape is the way to go), those put out a fair bit of light and get 3 siamese algae eaters, those will keep the algae in check like a boss.
If the tank gets enough ambient light getting some pothos is also beneficial.


4 Aug 2015
Duuuude, Did you see the thread on what causes BBA? It's a rite of passage in this forum. :)

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