First things first, I have no clue how much experience you have with aquariums so please bear with me if this is too much info or too basic.
Well, GSP's generally are aggressive fish and should be kept as singletons in the aquarium. They have a high degree of aggression between conspecifics and other fish, if left alone one will kill the other.
Please read the article I pointed you to in your Meet and Greet post.
library/puffers-in-focus/an-introductio ... d-puffers/
And for more info
ug.php/v/PufferPedia/Brackish/T_Nigroviridis/
As for Kumar's tail, there are a few things you need to do. The first step is to separate them.
Second is to make sure the water parameters are perfect. 0 ammonia, 0 nitrites, and 5-20 nitrates. How did you cycle this aquarium? Do you have the equipment to test these levels (API liquid test kits are the best)?
Third, you will need to get them in to larger tanks and fairly soon. A single GSP requires a minimum 30 gallon aquarium. This sounds like a huge tank for such a small fish but puffers create a huge amount of waste, both physical (from messy eating) and biological (natural body waste production). Puffers are extremely sensitive to their water conditions and having the high water volume is essential to their well being. Also a full grown GSP get to about 6 inches and the size around equal to a small Nerf football so they will need the space too.
Last thing on your GSP, they are not fresh water fish. GSP's are found in brackish estuaries, in brackish ponds, in brackish rivers and in near marine to full marine conditions. To keep yours healthy you will need to start adding marine salt to bring the SG of your aquarium up. There is a great, wonderful, beautifully well written sticky (written by me
) in this section if the forum on how to raise your SG and what is needed.
viewtopic.php?f=5&t=19348
And another great article:
http://badmanstropicalfish.com/brackish/brackish.html
This is a lot of info to have thrown at you and to digest. Read the articles and
feel free to ask questions. This forum is here to help and we
love to talk about our puffers and teach about puffer care. I'm sorry I had to dump all this on you but this is important info and I can tell you care about the little guys because you are asking questions. Most local fish stores do not have, aren't educated enough, or do not care enough to give out this information on the puffers they sell so the buyer that falls in love with the cute faces and ET like eyes has no idea what they are getting in to. You won't be the first and you won't be the last (unfortunately).
