If your tank is not drilled for the overflow, then just get a cheapo siphon box that uses u tubes. The u tubes will clear themselves of any air bubbles that get in there if you use the appropriately sized one, and you can use the in tank overflow box as a tiny refugium. Mine has a large growth of an algae similar to maiden's hair that I pull out periodically and dump into the tank. The lighting promotes its growth as it is over the siphon box itself as well as the tank. It also surface skims, removing the crap in the tank pretty well. Drilling can be tricky and expensive if you don't buy a "reef ready" tank. I have been thinking of upgrading my in tank siphon box to a larger one and sectioning half of it off for a legit refugium, instead of the mini one it has turned into currently.
I drill even my 10g tabks so I don't have to worry about hang-on overflows. I just use acrylic for smaller tanks and that makes them very easy to drill.
I am using a Tidepool overflow with great results. Am running approx 1400 gph without any problems what-so-ever. This unit is one of the most silent on the market too. My 200 Gal. tank sits right next to the boobtube, and can't hear the tank at all.
runs between 80-90 $.