go to the home depot or lowes garden section and check out the garden drip system fittings. i am pretty sure a small pump (under..say.. 150) will not be able to push enough water if your tank will be over 20". i had a 70 gph pump on a 18 gal tall tank and it barely trickled without any splits. i know all you need is a trickle for that setup but make sure the pump will push as high as you need with the fittings installed before you install it under the foam. i recommend a filter pump, its hard to clean this setup ESPECIALLY it you are doing it in an aquarium tank and have no front access.
this project turns out really well. a few tips though, use brown type II silicone it looks better if some shows through. and after you foam ( if you dont do it in small layers over a few days) let the foam sit for about 3 days because sometimes when you fill semi-large voids it will shrink back down about half an inch away from the wood and sides. just fill in the gaps where it recedes and you will be good to go.