 Simple one-piece overflow pipe for pico
Hi all,
After some reading and experimenting I decided to try and make a super-simple overflow pipe for my half-gallon pico in planning. As to why I want an overflow on such a small tank, it's part of an automatic continuous water change system I have planned. My previous nano crashed due to neglect, which I plan to prevent in my new pico by having a slow-drip system to change water one drop at a time, with excess water flowing out of the overflow.
My overflow plan consists of a single bent piece of flexible tubing (about 1.5cm diameter) shaped into two U's as shown in the attached picture. The U in the inside of the aquarium functions as an intake (I'll put a grill or something on it to prevent snails/etc from getting in). When the tank water level rises above the U, water flows into the intake, over and out of the tank to the second U, and finally out the output side. The second U in the output side serves to make sure that the output-side water level is (a) positioned low enough to pull/siphon water out of the intake and (b) positioned high enough to prevent the intake siphon from ever breaking. I initially had the second U too low, which sucked air into the intake and broke the siphon, but by having both U's at the same height, and by having the output opening lower than the input opening, everything seems to work fine (see picture). Beneath the output end of the overflow, I plan to have a bucket which will catch the overflow water and be periodically emptied (remember I'm making an automatic water change system, not a sump/return). During a water change I just pour/drip new water in - the excess water flows out the overflow.
Now, this design seems too good to be true. One tube as an overflow? Is this design safe? Is there anything I've overlooked? My simple tests seem to indicate that it will not lose siphon and that everything works. Am I forgetting anything?
Thanks and I look forward to setting up my new pico with automatic water changes! | 
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