Depending on how handy you are I would run a seperate circuit from your breaker box to that room if it is not too much of a hassle to get the wire there without having to fish through finished areas. That is what I am doing for my fish room.
If that is not reasonable I would look at connecting from one of the existing outlets and adding in a few more outlets in the room where you need them (first one in sequence preferably being GFI outlet). If you dont want the hassle of going through the walls you can run the wire through conduit along the side of the walls.
If you not comfortable with any of that or worried about electrical codes and dont want to look them up you pretty much left with only using extension cords, but even then at a minimum you should get them tacked up along the wall (off the floor a bit). Also if possible try to run extension cords from electrical outlets that are on seperate circuit breakers if you not using a breaker dedicated to the fish room that way you split the load on those circuits that also have other uses.
Finally I would make sure you have GFI protection no matter what option you go with. Personally think it nuts to have a fish room with many tanks and not have GFI protection. This can be done by replacing the circuit breaker(s) you are using with a GFI breaker. Or can go the cheaper route and replace one of the outlets in the series with a GFI protected outlet. One GFI outlet will protect all outlets on the circuit IF it is the first outlet coming from the breaker box. If you dont know which is the first outlet from the box it is probably just safest to replace the outlet that you will be using that way you are sure.
Sorry you probably got more feedback than you wanted there.
If that is not reasonable I would look at connecting from one of the existing outlets and adding in a few more outlets in the room where you need them (first one in sequence preferably being GFI outlet). If you dont want the hassle of going through the walls you can run the wire through conduit along the side of the walls.
If you not comfortable with any of that or worried about electrical codes and dont want to look them up you pretty much left with only using extension cords, but even then at a minimum you should get them tacked up along the wall (off the floor a bit). Also if possible try to run extension cords from electrical outlets that are on seperate circuit breakers if you not using a breaker dedicated to the fish room that way you split the load on those circuits that also have other uses.
Finally I would make sure you have GFI protection no matter what option you go with. Personally think it nuts to have a fish room with many tanks and not have GFI protection. This can be done by replacing the circuit breaker(s) you are using with a GFI breaker. Or can go the cheaper route and replace one of the outlets in the series with a GFI protected outlet. One GFI outlet will protect all outlets on the circuit IF it is the first outlet coming from the breaker box. If you dont know which is the first outlet from the box it is probably just safest to replace the outlet that you will be using that way you are sure.
Sorry you probably got more feedback than you wanted there.