I have been doing 40% water changes twice this week to give him some clean water, but my parameters seem normal.
1)Tank size: 40 US gallons. 4-5" Ceylon puffer on his own.
2)Feed once every 2-3 days on a mixture of mussels, bloodworm, gutloaded shrimp, krill, snails etc. 40% water change 1-2 times per week of 40%. Adding dechlorinator and marine salt to each water change. Temperature 80f.
3) What changes you've made in the tank in the last week or so. None that I can think of.
4)How long the aquarium has been set up, and how did you cycle it? - about 6 months. Had other fish in it before.
5)Water parameters: Ammonia 0 , Nitrite 0, Nitrate 10. Salinity: 0.010. (I test these twice a week to make sure they are normal).
Any ideas anyone why he died? Or is it just one of those things?