Thanks ThRoewer ��
If a new fish comes and looks good.
- Can I use formalin dip before put in QT?
- Can dip 2 or 3 fishes together?
- Just dip once then observe in QT in next few weeks?
It's what I usually do.
As for using formalin as a cure against ich:
The baths may only work in combination with tank transfers. Formalin is not able to reach the parasites in the fish's skin in the amount of time fish can tolerate it.
The long term treatment may work, but in that case I would rather go with Hyposalinity or TTM.
Hyposalinity is IME the easiest on the fish (and aquarist) and was so far for me 100% effective in clearing fish of an active ich infection.
The only fish you can't treat with it are
Chondrichthyes (cartilaginous fishes like sharks and rays).
For me the decision to go with TTM or hyposalinity depends on the fish and reason to treat.
For active infection of multiple fish I prefer hyposalinity with 2 transfers at begin and end of the 2 week treatment to make sure there are no preexisting cysts or protomonts ready to encyst. In general I add a third transfer after one week when all visible spots are gone. The last transfer is before ramping up the salinity.
Among the last fish I treated this way was a juvenile regal angel and it handled it perfectly fine.
Also, a covert tank will easily maintain the salinity for a week or two. Evaporation has also a much lesser impact at low salinity levels.
TTM I do preferably to treat single small fish that can be kept in small containers with or even without a pump or aeration to eliminate equipment that needs to be sterilized. I've done that successfully with small bluestripe pipefish who do just fine in a 2qt Lee's specimen container for easily a week or two.
Container Store Shoeboxes with $10 Jebao fountain pumps work equally well for small fish like damsels or juvenile clownfish. I rather go cheap and have a fresh set of equipment for each transfer than taking the risk that something slips through during in-process sterilization.
TTM is also the best preventative method to make sure the fish harbor no occult ich infection (= without displaying symptoms).
