Have you found anything that can coexist in there with him yet I’m still experimenting it’s starting to get a little expensive
99% of fahakas will not really allow for long term tankmates to be very honest!
From passed experience once they reach around 9-12” they can start getting aggressive towards tankmates as they learn that they are the boss...
Infact, i’ve even heard of 10+ year old fahaks who lived witb tankmates all their life, turning on tankmates over night killing everyone in sight...
So if you want a puffer of any sort, you should expect it to be a solo wet pet, coz even the friendliest of them (C.Asellus or T.schoutedeni which can somewhat be kept together) can be nippy towards tankmates...