Stoping the Syphon

[Murminator]

If you can right under the water surface of the return pipe drill a small hole and the nozzles can be under as deep as they want. I have a small hole drilled in my return inside the overflow it sprays a bit of water sideways but it's in the overflow so it makes no difference. On my freshwater tanks I do the same with canister fliters in case a hose pops off or blows then it won't drain the whole tank on the floor