So basically, one of my mollies in my 160L tank has got a white bump/spot near its dorsal fin, and he has started to turn a whitish colour near his mouth. Assuming this is columnaris or some other disease, I think I should transfer him to my 20L tank. This was originally my hospital tank, but I have decided to put a betta in it in a week or 2. So my question is that if I put my sick mollie into my 20L tank, will the salt I am going to add affect the betta I put in? (presuming the mollie recovers or dies). Obviously I will do a water change for my betta, but would this suffice? Would I have to change all of the water, which would then make the cycle it has been going through pointless and i would have to start the cycle again?
Thanks
Thanks
