I just had to have me a sump, I hated the look of a hang-on filter. No way I was going to drill a hole in my new tank! All the designs and do-it-yourself ideas called for a skimmerbox. "If I'm going to spend my time and money making my own filter why on earth would I only want to suck the water off the top?" I mean if I have a pump capable of moving up to 600 gallons per hour, just how many times would that top-water need to be filtered? Exactly how many gallons are on the top layer anyway? If my 55 gallon tank is 21 inches high and I filter the top 1inch of it, that means I am filtering about 2.54 gallons of water ... 226 TIMES AN HOUR. What about the rest of the tank?
If you skim the top and return it by a spraybar what is the use? the spraybar breaks up the surface and mixes it with the rest of the water, so exactly what are you doing. Removing gases? Alright if I have a 3 foot drop in a 1 1/2 inch diameter hose going to my sump, that's alot of turbulence and air-water contact removing those gases, and put a drip rail above the sump (more air-water contact) have a trickle-thru-media wet-dry sump (even more). "But these chemicals in the tank rise to the surface." How fast?, isn't your spraybar mixing them back down? What about all these people wasting their money on hang-ons and canister filters?
I figured as long as I have some sort of surface movement, i.e. spraybar, I could mix this "surface-water" back in the tank water and be more worried about getting the really nasty stuff out ... THE POOP! At the same time this invisible surface water would still be getting filtered and aerated along with the rest of it, at about 450-500 gph.
So I trashed the thought of the skimmerbox, and concentrated more on the bottom where all the bad stuff stays. Of course if all my fish made floaters I would have went along with it. Well anyway, run my siphon tubes to the nether regions. "it'll never work, it can't work, good luck". Well Horse-Puckey. It works.
The first step in building anything, skimmer or not, is to understand the concept of the whole thing.
Imagine siphoning water from your tank into a bucket. I'm sure you have all done this. Now raise the bucket up so that the height of the water in the bucket is the same as that in your tank. Still with me? What happened? The water stopped flowing, unless your hose fell on the floor. Now raise your bucket a little more, the water goes back to the tank. Enough playing, get the same water height again. What would happen if you started pouring water into the tank? It would fill the bucket up too. Imagine a hole in the bucket just above that waterline, now pour water in the tank ... OVERFLOW! Attach a hose to that hole and run it into another bucket underneath and put a pump in there, pumping water back to the tank. "What happens if the power goes out and the pump stops?" Everyone asks that. Well you are still holding the bucket aren't you? When the water level in the tank drops to the level of the bucket it stops, the level in the bucket stops when it gets under that hole you put in it. And everything balances out just like before.
OH by the way, where is your skimmerbox? Where is the hose in the tank? Don't need it, and the hose can be anywhere.
First off is the parts you will need.
I used 1 1/2" plumbing so I got 1 1/2" couplings (PVC conduit! not pipe threaded water PVC, you'll never get it to tighten on the washer), 3" tub washers (only needed one), Hose clamps (didn't need them, I heated my PVC and glued my drain hose into it), hang-on specimen container (or do it yourself with acrylic, this way was alot cheaper), hole saw (I used 2"), siphon tubes (2 should do it), some sort of hose that will connect with your pipes or just use PVC, a length of pipe that fits the couplings (I got this piece cause I didn't want an extra 7 1/2 feet to throw outside), and some sort of screen for your siphon tubes (wouldn't it suck to suck up a fish?).
Start out by drilling a hole in the specimen container. Remember to leave room to work and turn the couplings as well as have the siphon tubes fit.
Put the washer on the bottom of the container, screw the couplings together, I put the female on top because it was taller and came closer to my ideal water level. I glued everything just in case it wanted to leak, even next month, I don't want a flood. This is your standpipe, this controls water level. Hang it on your tank and draw a line where you want your water to be. Put a section of pipe in the standpipe and mark it about 1/4 inch below your water line. Take it out and cut it. Put it back in the standpipe but don't glue it; you may need to adjust it later. Now connect and route your drain hose/pipe to your sump.
Since I'm filtering poop I used alot of polyester-fiber (pillow-stuffing) in my sump for filtration. Bio balls? Not yet, I figure if substrate has bacteria being submerged so will this fiber being half "wet-dry". If ya got 'em, use 'em but remember get the poop out first. Change your top layer of padding often, every week or two. "Kinda hard to clean the water when it's running through poop, ain't it?" The hang-on filters, people change the elements how often? 2 weeks to 6 months?! Well that's alot of "stuff" the water is getting "filtered" through. Sure it's biological filtration, but nasty. Biologically poop makes ammonia, algae, nitrites, and contains toxins that weren't used by the fish in the first place.
OK I got this thing on the tank, where do my siphon tubes go? ANYWHERE YOU WANT I have one near the bottom and one halfway down.
I poured water in the box but how do I get the air out of the tubes? Don't drill a hole. Take your siphon tubes out and stick a piece of airline tubing in them, to the top of the bend. Put the siphon tubes back in place and suck the air out with your mouth, then just slide the airline out.
RETURN SIPHON? If the return is hooked to a spray bar you are ok. If it only goes to undergravel jets, or returns under the water line, just make a small hole in the return line just under the water level. This is so you don't siphon through your return line when the power goes out. It sucks air and breaks the siphon when the water level drops below the holes.
Start up your pump and be amazed. But don't go anywhere, if your water level gets too high, turn the pump off, take the pipe section out and cut a small piece off the end and try again. If your water is too low, pull the pipe up a little bit.
GURGLE? After doing all this I had gurgling noise so I thought of how a "Durso Standpipe" works and came up with a modification that would fit inside my contraption.
The gurgling noise comes from the vortex created by all that water running downwards; it sucks alot of air. Most people use a sponge prefilter to solve this, since I'm sucking off the bottom that filter would clog pretty quickly. So to keep the air out I used a cap from one of my wife's many hairspray bottles that would fit around the standpipe loose enough to let the water rush around it. Put a small breather hole in it, to break any siphon that may occur. It needs to suck some air to help all the water go down efficiently. The size of the hole you can experiment with. I cut some notches out of the top of my stanpipe for the cap to sit on, about 1/4 inch deep. This lets the water enter. You may need a longer pipe section to do this, because the new water level is slightly above the bottom of the notches. □