If my memory serves me right, if you put an aquarium on a community lot, go to live mode and take a sim you are playing and click on the aquarium, it should have the option to stock. I know I have been on a community lot before where I had put an aquarium and that option came up. I hope this is the case, I guess it is worth a shot. If that doesn't work, not sure this will, but maybe change lot type to residential, put aquarium in and stock it, then change it back to community, now whether or not the fish stay in the aquarium, I do not know. Will have to experiment with this one.
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