Al G- Be careful, I got flamed super hard for wanting to make some DIY vortech copys by folks on here...
Anyways, it turns out that makeing your own Vortch DIY copys is as easy as doing the maxi-jet to tunez conversion.
Thick acrilic disk with a Ti rod pokeing straight out of it, then a close fitting carbon fiber tube with an RC boat propeller slipped on the top of the tube. At the bottom of the tube you have a little 2" acrilic disk with 2 cutout for CD player lens magnets, or harddrive magnets, or really any little neodimium magnets positioned across from eachother on the outsides edges. Then stick a cover made from a plumbing bell reducer over the assembly just like what the pic you posted uses.
The next part is even easier, take a 2.5" PVC pipe section about 2.5" long. Stick a cheap RC car toy motor mounted in the center of the little 2.5" PVC tube. Stick the 2" disk with equally spaced neodemium magnets flush mounted into opposite sides to mirror the one you made for the propeller assembly.
If you didnt use super powerful magnets for the torque coupleing, then you might need to glue a couple of permanate magnets in approprate places on both halfs to ensure a solid sticking, but with the magnets I use, falling off seemed pretty much impossible, kinda like one of the very strong algea magnet scrapers. Put a thin little bead of silicone around the surfaces that touch the tank anywhere. Let that dry throughly to act like a vibration dampener and ensure silent operation. Now, the alignment is crucial to long happy and silent operation, so spend some time and get it dead nuts.
Also, the bearings in the cheap motor can also be noisey depending on what you got. Some small motors are really quiet with nice ball bearings and you cant hear them at all. Others sound like annoying whiring sounds, but I would say still more quiet that most closed loop pumps. Anyways, then you just supply it with power from whatever source you want, old computer powersupplys work great as a controler with the addition of a little pot interfaced with the voltage regulation circut for speed control. That way your powersupply can stay under $5. There are a zillion other ways to power them, or make your own controler and wavemaker or whatever, but its 3:52am and im tired of typing.
But yeah, thats how to DIY vortechs for about $35, depending on the quality of components you wana use.
Now I supose I will get flamed to death...