he did the first day i bought him and hasnt since.. but they will do that alot . no worries.. and as far as keeping them with other fish they say u should not but i am going to add him to my 240 when hes big enough with a 24 inch arrowanna/dorado/wolf fish/pike . i think it can work out in some circumstances but u have to have very tough mean fish to go with him like i just mentioned.. its a experiment for me cause i have kept all these other fish but this if the first for a fahaka for me.. so ill let u know how it works out. It all depends on the actual fishes personality.. my buddy has a pignose puffer which are very mean as well and will devour a large crayfish at site but i gave him a gold garami which he threw in with the puffer 6 mos ago and there doing fine with each other.. go figure there in a 10 gallon at that too... and he only feeds his puffer every 2 or 3 days...