Formalin.

[Microman]

Will the use of treatments containing Formaldehyde gas such as Formalin from Amquel affect filter bacteria.
For fungal infections is it best to treat as long term bath or short term dip.
Thanks,
Mark...

 

[fishgeek]

most medications will affect filter bacteria , the real question is will thi affect filter performance

the straight answer is not simple
every study i have seen has differing results

the basic premis is that yes medications will affect biobacter in the filter unit
this is dependant on medication- type/concentration/flow past biobacter
also the function of the filter is less likely to be impinged if the filter volume or more correctly surface area for biobacter colonisation is large and filter is old
basically assume half of he bacteria are killed , if your have a four fold excess(for biological filtration) then it doesnt affect filtration if you have just enough then you will have ammonia/nitrate spikes as in a new setup

if you are particularly concerned the remove filter media and store in bucket of tank water for a day or two and just run mechanical filtration

 

[Mike Wise]

I have used formalin/formaldihyde for many years without too many problems. At 2 drops per gallon (1 drop / 2 L) - 37% solution is standard, I believe - it is effective against many external parasites, but does not seriously affect the biological filtration. It is important to know that it is less effective in an organic-rich (a lot of mulm) aquarium than in a bare tank. The formalin rapidly oxidizes with organics. Formalin is also a known cancer causing chemical, so try to avoid getting it on your skin, or breathing in the vapors.