So I made a boo boo when i designed a custom background for my 55g. I left a single slot in the back of it for the tank to "drain" into the filter. I had a piece of tube from something that went about 8" down into the tank and about 2 outside and hangs over the side. I wanted to use it because it had a nifty "jet" right next to it for feeding back into the tank from a filter set up. I believe it would be similar to what is used in a sealed canister filter set up. I wanted to make my own wet dry filter and a refugium for my cichlids so they would have the benefiet of live plants without being able to destroy them. The problem is I did not think of how a syphon continues even if the pump doesnt and also how hard it would be to "match" the flow ov a pump and a syphon. this led me to realize i needed a full blown overflow setup but that it would not work with my "Hide Everything Background" so after much cursing I think I have a solution!
The point of 2 boxes in an overflow system is to have a water "level" between the 2 that can not drop so as to let water exit the tank in a controlled manner that will not continue if your pump fails. What i am thinking is a hose from a traditional overflowbox outside the tank runs into the tank as low (deep) as you want it. the only trick is the box outside has a raised "drain" hose inside it at the level you want the water inside your tank at. the syphon hose from the tank to the box will of course be below the desired water level on both sides thus maintaining a "primed" syphon in the event of a power outage/ pump failure. ergo the syphon hose equalizes the level of your tank and the outside box and when the level in the tank rises the level in the box rises thus overflowing the way a typical stand pipe would in a tank of that style. this would allow you to syphon water from lower in the tank where you need it (colder dirtier water) unlike a typical overflow box. it would also make the system more simple and cheaper as well. if your pump shuts off it of course can have a traditional "syphon break hole" in the system if you arent using a spray bar so that it does not backflow (syphon)to your sump. I have attempted to explain this before in another forum but something was lost in translation so feel free to ask questions. If this is already being done i am not taking credit (unless it hasnt lol) I just could not find a single example of this anywhere, nor have I tested it, so feel free to enlighten me if I am missing something!

Yes ,all it takes to break the syphon is a 1/16" hole at the highest point of the return hose..Sounds like we have done the same type of system,everything is hidden within the foam backdrop,The return from the sump is at the bottom of the tank shooting up towards the outlet box.I had to downgrade the diameter of the out box tube,from 1 1/2" to 3/4"
because it was real noisy and was aerating the water to much.......

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Mt.Shasta,CA

Yep, works pretty well! I have a very strong pump but after lowering the tube to the sump lower than I actualy wanted the tank level at a little the syphon picked up speed and everything has been doing nicely! I should post a video I suppose, in all probably cost less than $10 for the whole overflow setup. the pump was $40 and the fish love it.
Only difference I see is that I am using a spray bar and syphoning from near the bottom of the tank so i guess its a little more flexible this way as well!