Growing a nitrifying biofilm.

Belgian Anthias · Jun 17, 2018

It may be a very simple question but it is one for which I have no straight answer:
" Do we need light for growing a balanced nitrifying biofilm or is a bio-filter best kept in the dark? And why?"

glb · Jun 17, 2018

Belgian Anthias said:
It may be a very simple question but it is one for which I have no straight answer:
" Do we need light for growing a balanced nitrifying biofilm or is a bio-filter best kept in the dark? And why?"

I’m not sure what you mean by nitrifying biofilm. Do you mean the bio-filter itself??

mcarroll · Jun 17, 2018

Belgian Anthias said:
It may be a very simple question but it is one for which I have no straight answer:
" Do we need light for growing a balanced nitrifying biofilm or is a bio-filter best kept in the dark? And why?"

No light needed. Dark/light doesn't matter...at least not much.

mcarroll · Jun 17, 2018

Uh....that said, if you're just starting a tank, IMO it's best to leave it fully running, but dark for at least a few weeks before lights-on.

(Keep NO3 and PO4 above-zero and in-range during this time, if needed.)

Belgian Anthias · Jun 17, 2018

A nitrifying biofilm is a very complex community. It contains bacteria and archaea. Only a small part is in fact occupied oxidizing ammonia to nitrite and nitrate. Most of the bacteria are recycling dead biomass, +- 40% of the bacteria in a nitrifying biofilm are using an anaerobic pathway of which some are denitrifiers. Part of the population may be light depended. In what extent the light sensitive bacteria are needed to maintain a healthy nitrifying bio film? Or are they present just because there is light. In what way they influence the oxygen consumption which is a primary factor in the composition of the film? For the nitrification and denitrification capacity?
A nitrifying bio-film growing in the dark will have an other composition as a bio-film growing in light conditions, conditions which may influence the nitrifying and denitrifying capabilities of the biofilm.
Keeping the bio-film or bio-filter in the dark will certainly prevent it will be overgrown by algae.