Here's my 55's fuge. The water line you see is about as full as I myself will fill it. One of the bonus features of this design is built in display tank flood protection. If you look in the far right chamber you'll see my return pump. The chamber is comletely sealed with silicone from the rest of the 'fuge. In the event my overflow siphon breaks, my pump can only return the contents of that chamber up to the top of the baffle. In this case, it can only pump 1 gallon of water into the tank before the pump runs dry. If I pull more than 1 gallon out of the system the pump starts sucking air, and won't pump in more water until the siphon is started again. I keep the display about 3/4" below full so it can absorb that 1 gallon flood with no problems. The closed loop using a hob
overflow prevents the fuge from backflooding if the pump fails. I keep my return line right at water level, so in a power failure it only backfills about 1.5 gallons which is easily absorbed by the fuge. You have to trial and error to get the adjustments right, but after that you don't have to mess with it. Having a quick finger on the power button is a must
Tyger: I have a 6 inch sandbed in the display tank and a 2-3 inch sandbed in the center compartment of the fuge. There is also a large hollow rock inside all that algae. I also keep about a half dozen snails living in there to keep the substrate stirred. Poor little fellas are nocturnal by nature, but live in 24/7 light. They seem to have adapted well to it tho'
Ok, I give up. Stupid picture posting %*$%*^^%)& never works for me for some reason.