Green spotted puffers stomach turning black?

Start with a cycled tank if it’s not cycled you shouldn’t be owning a Puffer fish quite yet. Patience and proper planning leads to the best life and care of the fish you love and want to do its very best to excel.

Always have the proper tools to test your water, especially with intermediate to advanced fish keeping like GSP’s. API Freshwater Test Kit, phosphate, GH, and Sality tester are key to making sure you got it covered as nature did. Check Salinity or Specific Gravity, pH, ammonia, nitrite, nitrate, Phosphate and General Hardness (GH) results. Even if the tank looks clean any traces of Nitrites and Ammonia can cause serious problems with your fish. Doing a 50% water change will help if that is the problem. Getting a good water test kit is key (i use API brand liquid tests).

Also puffers are ususally wild caught and he may hav internal parasites. These nasty parasites will often attack your fish when a change is made and he is stressed such as moving him. A good indication that he has IPs is his belly will go away soon after he has eaten. He may also have stringy looking poo. Is he eating good or at all?

Sometimes puffers will change colors depending on their mood or if they are sleeping..However it can also be an indication that your puffer is ill, stressed, or living in poor tank conditions. It can also be a combination of these problems.

Coloration
Green spotted puffers have an attractive coloration that attracted me to them originally. Under normal conditions, the back of the puffer is a deep green with black spots all over it, with a white belly. This is normal coloration, but like the chameleon, the puffer can change its colors as he or she sees fit. Sometimes instead of a creamy white, they will have a completely black belly, and the spots and colors on his back will fade to very pale. He will also sometimes have spots on his back and a black belly. If your fish has a black belly all the time, he is most likely sick, but if he changes all the time, he’s a healthy little guy.

Behavior
At times mine spend a lot of time sleeping at the bottom of the tank. That is, until he sees me walk into the room, then he will swim up and down on the front of the tank until I feed him or pay some sort of attention to him. The rest of the time, he swims around his tank exploring and nibbling at stuff, every once and a while ripping off chunks of plastic plants and filter downspouts.