For a DIY overflow to work well, how far below the tank would you think the sump needs to be to allow gravity to do it's thing? I'd like to set one up on our ray pond, but it's sitting directly on the floor. My backup plan if I absolutely can't get this idea to work is going with a Laguna Pressure Flo pond filter, but it's got that ugly Max Flo sphere that would need to be in the aquarium, and I'm just not sure I want to go that route. It'll be a pain to cover up! I originally wanted to run FX5's on it, but they need to be 7.8" below the water level since it's a gravity fed filter, and they would be sitting right at the water level. I've run into a filter conondrum 
If you've got a pond on the ground, what's your preferred filtration method? My rays are growing quickly, and I'd like to get them out of quarantine now...but my filter problem has me stumped!!

If you've got a pond on the ground, what's your preferred filtration method? My rays are growing quickly, and I'd like to get them out of quarantine now...but my filter problem has me stumped!!