Even a 125 may be too small for the shark egg. Even that black edge eel you got there is pushin' it, everywhere I've looked online (I did some special research just for you) says that they need at least 125 gallons of water, you don't even have half that! The only eels you could have in a tank that small would be a snowflake or ghost moray. You really need to think about that tank and do a lot more research because that seahorse will likely die in a tank like that, it's hard to tell from the picture of it, but it looks like u have somewhere between medium - strong water current in there when they need a low water flow, and the shark egg is definetly not qualified for a tank that small and to be compatible with peacefull fish such as a seahorse. I'm not sure what you'd like to do, but if your really into seahorses, that tank would look awesome with a couple more seahorses and some pipefish! Just make sure you get all your info straigiht on them. Let us know what you decide! :yes: