April 2010 - Kitchener Waterloo Aquarium Society

A P R I L 2 0 1 0Once in place, the following days were taken up withunloading, unpacking, and settling in. Those days turned intoweeks and then months, as the few fish that were brought withus found their way into the smaller, easier-to-set-up tanks. I didmanage to mail-order some Poret open-cell foam from Stephan,but otherwise our “big screen aquarium” sat in the living room,empty and dejected. Who knew, tanks actually have feelings...Finally during the 2008 holiday break, I found time to really getthe project off of the ground.The massive 4” thick foam sheet was actually quite easy towork with. A straightedge and sharp knife were all that wasrequired to cut it to shape. Its rigidity meant that I could sizethe sheet to be slightly larger than the tank's internaldimensions, and it would hold itself in place quite securely.This was the first and easiest step to complete. I would cautionagainst using foam sheets or pieces that aren’t specifically madeor marked for use in an aquarium―foam designed for airfiltration may be impregnated with mold inhibiting chemicalsthat can wipe out aquarium fish.Next came the PVC manifold design. I decided that 3/4” PVCwould make a nice balance between size, ease of burying undersubstrate, and availability of parts at the local hardware store.After picking up a few T-junctions and elbows for measuringpurposes, I decided that I could fit 4 pipes down the length ofthe tank. The vertical connections to the pumps and risers ateach end could be made between the first and second, and thenthird and fourth pipes. Eight T-junctions, 4 elbows, and about25 feet of PVC pipe later, I had my manifold base dry-fitted intothe tank bottom. I cut slots for the manifold pipes into mysponge sheet so that it fit tightly down to the bottom tank glass.water at all through the tank itself. I looked for some backflowpreventingcheck valves in 3/4” PVC, but could not find anythat were small enough and had a low enough forwardpressure drop to work in this situation.This constraint led me to settle on using manual ball valves sothat I could isolate either pump from the manifold at will.Fortuitously, this also led to another significant designimprovement of the powered manifold system―active tankdraining. If I could keep a pump from supplying therecirculating manifold, then I could redirect its flow up and outof the tank and make water changes a heckuva-lot faster andeasier.I settled for a 3-valve setup. I placed one ball valve betweeneach of the 2 pump outlets and its manifold entry, and then athird valve formed a new vertical riser between the outlet of thepump closest to the front of the tank and a threaded PVC fittingwith screw-on end-cap, whose top remains below the tanksurface. I briefly considered putting this riser at the back of thetank, but in the end, ease-of-use outweighed aesthetics in mymind. Besides, I'm an engineer, I want to show off my work! Ibuilt a separate PVC drain adapter which, after the end-cap isunscrewed, screws into this riser and uses a faucet-style valvewith garden hose fitting at the top to carry water out of thetank.Now on to the pumps. I focused on units that were compatiblewith PVC fittings, and was looking for something with a fairlyhigh flow rate without breaking the bank. I finally settled ontwo Danner Supreme Mag-Drive 7 pumps, rated at 700GPHeach. I figured that in reality, I would probably get 600 gallonsper hour from each pump after losses in the plumbing. Thepumps had 1/2” male PVC fitting threads, so I used a threadedadapter and a short piece of 1/2” PVC to reach a 3/4” PVCadapter which connects to the rest of the plumbing.I decided to go with two pumps and two return spray-bars inthe design. Technically the manifold could have been created intwo halves, with each pump powering its own spray bar viatwo PVC pipes across the bottom of the tank. In the end Idecided to plumb them together, for the sake of structuralintegrity and ease of final placement and assembly more thananything else. But this design had one significant drawback―iffor whatever reason one of the pumps was not workingproperly, the second pump would simply push most of itswater backwards through the failing pump, rapidlyrecirculating water behind the sponge but not pushing muchI removed the stock foam pre-filters from the pump inlets. Iwanted to save them the embarrassment of sitting, near useless, 17