I'll tell you what, go to the person with the tank, and ask them because honestly unless the species are very carefully chosen, this tank will not fly. As for the water, I see it like this. First, you said its a 55 (lets say 60 for ease). That means half is alloted to water specimen, 30 gal. That means there is about 15 gal of water in there. Which means you get a filter similar to a Fluval 1 or a Wisper 22 or whatever. In any case, niether of those filters can suck up crap, thats why they suck for turtles. Not even an Aquaball from Eheim would do a very good job in such conditions. You need a large outside the tank filter. I have yet to see one for less than 30 gallons. You will create massive currents with that filter, not good for the fish imo. Bacteria that I speak of is ammonia, which will be present if the filtration is improper. Ammonia levels will skyrocket if reptiles repetedly drop crap in your tank. You will need to run like 4 small filters to keep up or 1 outside the tank (which I already discussed). Water changes are a [bleep]...if you havnt owned a tank ask someone who has to do a few for you so you get the feel for how crappy it is. All in all I cant begin to list the problems with the fish and I dont even have a clue on what you will keep there....This whole idea is insane, honestly. If you think that this will work, map it out and run it by me or someone else here because I cant see a way to make this work without unatractive equipment and dull lizards. There is several geckos that live by the sea. One of those genus are the leaf toed geckos which I believe are quite expensive. Try and get in touch with the guy who did this and tell me how he did so and how his animals are doing because this seems unreal to last for long. This is no BS opinion either, ask around. I have read many books on seperate lizards (since I dont have [bleep] to do at work) and this doesnt fly from my research.