Chloroquin DiPhosphate repeat dosage?
 

I am treating velvet in my fish only tank with chloroquine diphosphate and have done some research over the internet. There are several contradictory informations regarding to the dosage and can someone help me clarify?

Overall the recommanded dosage is between 40-80mg/gl but what I am confused about is the need for repeat dosage of 40mg/gl weekly for 3 more times? Some said it is necessary because CP act the same as copper will become absorbed by the substract or somehow broken down by the bacteria in the tank and repeat dosage is needed. Some said it is very stable and substract will not have any impact on the dosage.

Have anyone had any experience on CP especially dosing to FOWLR display tank? Also many says CP is sensitive to light and all light must be switched off and some says it is only sensitive as powder and once in solution the light will not affect it too much. Which is true? I am talking about moderate led light not strong metal halide lighting.

The repeat dosage is for Ich treatment, not Velvet. In non sterile settings (display tanks) where high levels of nitrifying bacteria are present, there is a chance it is broken down more quickly. Without a Spectrophotometer you can't measure the CP and those aren't fiscally responsible to buy for most of us. Its a very forgiving drug and can be overdosed without much, if any harm to the fish. I have dosed my DT with CP for 3 weeks straight every 5th day like Nogas book mentions without water changes before dosing and the fish never acted like it was in the water. The powder is sensitive to light but the solution isn't and there is no need to turn the tank lights off.

I lost a kole tang and lemonpeel the next date after CP dosage.
I suppose my lemonpeel and kole tang were too late to be saved from velvet then. Thanks for the input they are very helpful.

Since your dealing with velvet I would suspect that is what killed them and not the CP. Certain wrasse, pipefish and seahorses don't do well with CP

I agree. Haven't had any side effects with Tangs using CP, IME.