loganj said:
I wonder if the alk has been creeping down over time? It might allow pH swings...especially at night. My alk usually stays at about 5.0-5.5 meq/l. I'm thinking that ammonia/nitrite should be 0 also. If you're having to siphon out uneaten food every day, it might be a combination of too much bio load and some overfeeding.
Logan J
I wholeheartedly agree with this. The fact that you need to do that much of a water change so often is a problem, IMO. In a mature, properly stocked tank, you really should not have measureable ammonia, and certainly not to the extent that it would be considered the 'normal' reading for the tank. I definitely think it is time to remove some of those fish, and get a new test kit which should be used regularly.
I do not believe the chocolate chip star had anything to do with the demise of these fish. To my knowledge, they are not able to secrete any poisons...and if they were, it would kill all of the fish in the tank (similar to sea cuke toxin). Though predatory (and certainly open to eating dead fish), they are not capable of bringing down so many healthy fish. I think you definitely need to look to water quality and overstocking as possible causes for this loss. Were there any marks on the fish at all?
I agree with the possibility of a pH drop, or other fluctuation that may have caused trouble. Did you do anything out of the ordinary with your water change? Stir up anything? Did you add anything other than the star the other night? Any other fish?
As you learned (the hard way I am afraid), seastars and triggerfish do not make good company. Triggerfish are a natural predator of seastars and brittlestars in the wild.
FWIW, these stars are not reef safe. In the wild, they are rather opportunistic, eating algal films, sponges, mollusks, etc. In tanks, they will often eat corals, anemones, snails, clams, dead fish, etc in addition to 'grazing' on LR. They do quite well in some FO tanks that house messy fish, which result in a lot of wasted food for the star to scavenge. Their braod diet make them relatively hardy and popular choices for hobbysists, but there is definitely a risk that they will eat something valuable. They are not the best tank mates for FO tanks with triggers, puffers and large wrasses (all of which are natural predators).