My powder blue tang just died (6/29). I got him on the 7th of June. He is small and therefore young. My ammonia, ph and NO2 levels seem normal. All my other fish seem healthy as well. The fish seemed healthy right up until this morning when I saw him laying on the sand in my cave (upright but just sitting there). The only recent changes I've made is that this Saturday I rinsed off my filters and added a new algone packet. Can my fish just die for no reason at all?
I have actually had this happen with PBT, particularly smaller specimens. This is misleading though, as I have had greater success with smaller fish than larger, overall (with PBTs). In a string of purchases from live aquaria a couple months ago, powder blue tangs (small) came in very thin with sunken stomachs. I am pretty good at getting fish to eat, but to me this was irritating because I know this means they're more than 50% out the door at this point (dead). However, I got two of the three to eat. (I tried two prior to these three that did not eat at all and were gone in 4 days). One of them died after about 5 days without warning, the other one starved because it refused food, and the most healthy of them had a seizure immediately following eating after about two weeks of thriving.
My newest two I purchased after that also had sunken stomachs and were thin/emaciated. However, they're both doing well and I have had them now for over a month. They're seemingly healthy and very fat.
So I am not sure how helpful any of that is, but the answer to your question is that you're not the only one that has had sudden death issues with small PBT.
That said, this is a fish that can almost NEVER be kept long-term in a tank that has ever had parasites (even ich), or is being "managed" with ich. I have an ich-managed tank that is very successful and I have kept many tangs in tanks with ich but they get it, and then it goes away on its' own with proper feeding and good water parameters. Acanthurus tangs, especially Powder Blue and Achilles, are NOT able to do this. 99/100 will perish in a tank that is managing ich (has ever showed signs at any point, without being run fallow and all fish and incoming fish treated for ich properly before being added to the tank in the future).
I have kept Hippo, Yellow, Purple, Kole, Desjardini Sailfin , Blonde Naso, Naso, and regular Sailfin tangs in tanks with ich for years with minimal issues. Again, none of those are acanthurus tangs. I am in no way condoning ich-management, as it requires good husbandry, lots of experience, and is still not very ethical treatment for tangs, and other more fragile species.
To any reader, if you wish to jump in to the arena with Acanthurus genus tangs, be prepared to QT all new fish, run your tank fallow for 72 days prior, and treat all of your existing fish prior to addition. Once they show signs of ich or other parasites, it can often be too late and they may not survive treatment.
However, if introduced and treated in disease-free quarantine or hospital tanks properly, they can be very hardy, beautiful additions. I've actually had much better luck with Achilles tangs than Powder Blue tangs, even with proper hospital/quarantine procedures. I currently have two very healthy achilles tangs, two powder blues, one powder brown, and a sohal tang (all Acanthurus tangs).
