Overflow boxes

Instead of the U-tube, use some tubing that has smaller diameter.  Something about the water flowing faster through that small tubing won't let air get trapped at the top of the tube. 
You can go to youtube.com and type it in and watch some pretty cool stuff that people have done.

 

In general, I think overflow boxes are the devil, but if I had to use one, I'd probably go with a CPR overflow w/aqualifter pump for a couple reasons:

1) The portion that sits in the tank is very low profile compared to most overflows and is therefore much less of an eye sore.
2) When used in conjunction with a cheap AquaLifter pump, the CPR has the unique ability to re-establish it's own siphon.

If the AquaLifter pump is maintained properly (aka cleaning it every so often) this is the most reliable overflow system there is. But be warned that without the aqualifter pump (or if the aqualifter is not maintained properly) the CPR's will have a hard time maintaining a good siphon.

-JB

 

Agreed with JB.

1 problem is that I have seen a piece of fish food plug an aqualifter.

If possible drill it & put a bulk head in it.

 

i'd just drill it, i do have 1 tank that is still running on a cpr/aqualifter setup that has never gone wrong. but aside from that i've had bad experiences with overflows and have drilled all my other tanks, and i'm replacing that tank with a drilled tank this month. i even tore down a reef tank and set it back up just to drill it last year, it took 6 hours from beginning to end, but it was well worth getting rid of that overflow.

 

Well, after just cleaning up a mini-flood tonight, I'd say drill your tank I have a cpr and an aqualifter, BUT I haven't been good about cleaning out the actual Aqualifter, just the tubing........... otherwise it works fine, although the tubing/opening are so small that stupid little things can clog it up. I once had one of the styrofoam beads somehow get into the tank water and sure enough, it got sucked up into the Aqualifter and plugged it all up. I ended up re-drilling the hole slightly bigger where it exited the overflow and entered the tubing.......

 

I went through two Aqualifter pumps on my 30g before I gave up on the overflow and sump system, and just went to a large penguin hang on filter!

Not the best setup, but I don't come home to 10g of water on the floor either.

My 30g reef has been up for 2yrs and is doing just fine.

But I would agree with these guys to get your tank drilled and save you're self allot of grief!! 

 

Drilled is always better, but if you use an overflow get a CPR with an Aqualifter as mentioned. I have three of these setups running as well as one homemade overflow with an Aqualifter. A few keys to avoid disaster:

1. Get the add on filters for the Aqualifters and keep them cleaned
2. Buy an extra Aqualifter for an immediate backup, they are only 10-15 bucks online
3. Buy the diaphragm replacement kits or replace the pumps, the kits are $3
4. Check daily for output!!! If it isn't steady stream clean the filter. If that doesn't work replace with backup pump. Clean the pump and test. I can usually tear them down and spray them out and they work great. If they have a hard build up on the diaphragm I replace it. Do not ignore the pump if it is only dripping get it fixed now. When I decided to ignore this for a few days I got a call at work, "come home and clean this up!"