FF, yes, you're totally right. I forgot about this:

That may be it, thanks all

Unless they are fairly large the anti siphon holes can and will eventually get clogged over time. I used to have them on my return nozzles to break siphon and had to increase their size a few times until I reached about 5mm I think. Even that clogged over time with various algaes :(

Anyway, as mention already you can guarantee their effectiveness by regularly checking them. I on the other hand got fed up with that added maintenance. It was just "one more thing" to pay attention to, maintain and support on what is already a complex system.

Anyway, just thought I'd throw that out there.. You know, since Mr. Murphy is such a big fan of out hobby and all :neutral: In the end I just let them clog up for the last time and instead built a bigger sump to support the extra 3 gallons to siphoned out from the return nozzles.

This is what I am doing... still waiting for my hole saw to show up. I will be dividing my return into 2 flow accelerators coming through the back wall.
My overflow's final drain point will be slightly lower then this so it will not add any "extra" water to the sump if the pump fails.

http://i737.photobucket.com/albums/x...one/Return.jpg

What pump will you be using with that eductor?

It's a 1" line that gets split into two 3/4" flow accelerators. I will have two of these for my 320g tank. The pumps I have are 1250gph but with the 6' head it's about 1000gph per pump... I have two pumps.