Not trying to spam up your thread, but wanted to show you what I did with them :)
This one isn't done, but it has a heater now. I just wanted to show you what it looked like mostly empty, or simply decorated.
ETA: I haven't used the filters for the cubes, but I think I'm going to try them out. They seem to work much like a sponge filter. They look like tiny Whisper internal filters. I've read online that the air pump dies tragically after a few months of use, but I will try it and let you all know what's what :)