clownfish not doing good

Nitrates certainly are not toxic to fish at 40ppm. However, sometimes nitrates are indicative of another issue that is not tested for. In that regard it could be a surrogate marker for something else. What is the source of the nitrates? Is something degrading that could be releasing other toxins?

That said though, if your other fish and especially inverts seem to be doing fine, I doubt it's water quality as clownfish are pretty bulletproof in this regard.

Could be some type of infection that just isn't presenting any signs. This would be my guess, as obviously something had to kill the other clown. These are long lived fish, should live over 15 years.

It also isn't uncommon for clownfish to be moody and sit in a corner. It could just be discontent with the environment. I do actually believe that the fish could be disoriented without his mate.

I would focus on why the other died though. Is there another fish picking on them? This would also do it. Also, what are you feeding, maybe it isn't what is needed. Have you tried soaking food in garlic? this can help get the fish eating.

 

If you continue to have issues with the nitrates, perhaps consider looking into a product called Microbacter7 (mb7). I have used it in the past with excellent results.

 

Great point I really like mb7, and have had good luck with it. Much better than a water purifier as the bacteria, helps to ensure a diverse bacterial population, which may help builds up the denitrifying and denitrifying capabilities of your system. A purifier will do the opposite. It will remove the food source and possibly inhibit your bacterial population. I think it's pretty safe to say that ensuring a stable bacterial population is a much better long term solution.

 

Just an update I have gotten him to eat finally. He munched on some Spirulina Brine Shrimp 2 days after the Prime was added. I was pretty happy, it didn't much but it did eat. It is still in its corner and won't swim around. I have started to doing 5 gal changes every night in hopes of getting the nitrates down. I have gotten them down some not much but some. I have noticed that the fish and corals are doing better my fish are always swimming around more now, and not just after they eat. I also wanted to thank everyone for the help. I have not been able to find the cause of the one clown death.

 

It is depression. I had a pair a few years ago and one died. The day after he died he started swimming at the top of tank near my overflow. He eventually died from lack of eating. I had tried multiple brands, live brine, frozen, flake...everything. He would always eat but not enough. He died 3 weeks later... I was so frigging pissed.

Hope all is well and he pulls through.