If there are no signs of velvet/sickness, is it safe to return fish to display tank?


New member
I'm currently scratching my head at what I'm dealing with here.

In one of my shallow 60g tanks I currently have a yellow assessor, a sand sifting goby and a juvenile sailfin tang (temporarily moved from the 100g). I was under the impression that this tank has ICH as a few months ago my fish had visible white spots on them. Behaviour and feeding was normal so I just watched and waited and they disappeared.

I recently added a clownfish and almost immediately he was swimming erratically daily back and forth across the length of the tank and hanging out mostly towards the surface. I had a close look at him and he was absolutely covered in white spots. I remember reading somewhere that this is more of a telltale sign of velvet if there are too many spots to count. It did sort of give him a velvety appearance although he is almost completely black so I may be confusing ICH with Velvet.

I've since relocated him to a small quarantine tank and have been giving him occasional FW dips. He has been there for approximately 2 weeks and shows no signs of spots anymore and is eagerly eating.

I'm at a loss however as everything I've read says that velvet is a fast killer. My DT fish appear completely unbothered and the tang (which are supposedly magnets for these diseases) seems to be the fattest, happiest fish there. He will readily eat live foods, worms, clams, seaweed etc etc straight from my fingers. I really thought clownfish were supposed to be the hardy fish here! I am concerned considering how small 60g may be for him despite him being a juvenile so I'm hoping to get him back into the 100g ASAP.

If I am truly dealing with velvet, wouldn't my DT fish have already been affected by now? I'm surprised that it is a clownfish > tang that is affected in particular which is another head scratcher. I believe the clownfish had spots for a few days before I removed him when he was absolutely covered head to toe almost overnight.

Does anyone have any suggestions or know what I could be dealing with here? Do I simply have immune fish in my DT? Should I take a chance and return the clown considering he has no signs of sickness? (Another head scratcher considering I have not treated him at all, simply a few FW dips). I feel like I can safely assume my DT is infected with either ICH or velvet.
I think it's worth mentioning that my parameters are all good, however nitrates are undetectable and calcium is ever so slightly raised. I don't dose, and only use NSW and RODI so I'm not sure how that happened, if that helps. I do 20% water changes weekly.
Fish can have apparent immunity to ich/velvet. Doesn't matter who had it first now as whatever the clown had is in your DT. Only way to rid it is to take all fish out of DT and treat in QT for 6-8 weeks leaving DT fishless.

Velvet responds to FW dips but ich doesn't.
Fish that slime heavily---and clowns may--- may pick up sand grains. Do you have black sand?
I did some reading and found that the way I’ve been handling diseases sort of follows Paul B’s method for having an immune tank, feeding live foods etc and so far it seems to have been okay with my long terms fish, although the clown being the newest addition could explain for why he’s the only one that was affected.

Theoretically if the fish in the tank are immune, wouldn’t that mean that there isn’t really a host fish for the velvet to reproduce? Provided that I keep the susceptible fish out (clown).

And sk8r I just have white sand :)