Hmmm....I can't get a good enough look at it. I can't see where the expansion tray is to cool. That's the key part for any custom use. Here's a Color picture
. The solenoid valves are exciting too!
I see three possible problems:
1. Does not indicate if refrigerant is already in the system.
2. BTU cooling is good, but not awesome at only 200btu from what I've seen(only window AC's). Two systems in a well insulated cabinet could lager a good size though. I bet. Read this to find out more about BTU in cooling terms
but keep in mind we're not trying to cool 75 gallons, only a 1/5th of that! BTW, that link is a great read.
3. Possible Small or weird tray to expand on.
It's duty cycle may also be much higher than others for all we know. so #2 may be a moot point.
BUT, based on the other parts it's coming with, I'd at least check and see how much shipping is. For me, it's $28.81., so ~$50 for this thing. Part of me want's to get it to check it out, the other part of me wants to just keep an eye out for an window A/C unit.