Steve, Don- Some guy measured ~1300gph from his maxijet 900 mod. Do I remember the propeller he used? No, I'm sorry I dont. From my fluiddynamics experience, I can tell you that the inlet slit shape design is going to be of equal if not greater importance than the propeller P/D.
For those of you who must be thinking "why would any manufacturere use an impellor for a pump if a propellor works so much better?"
Impellers are capable of high heads, as well as omnidirectional rotation capable.
For in-tank circulation, head becomes irrelivant, and with the clever way of passivey ensureing proper rotation direction, the directional propeller problem is also solved.
Just playing around, I put a 2.75" RC plane propeller suspended by simple hole /bearings in the end caps of a chunk of 3" PVC. the PVC had a large notch section taken out of the bottom and top right above the end caps. I powered the shaft with direct coupleing to an RC car motor connected to a moddified computer powersupply.
So, the PVC end gets dipped down in the water, the motor obviously stayed out of the tank at the top.
It was just cheese dicked together as a temporary experiment, but I would guess it was easily exceeding 10,000gph (yes, I realize that means 3gal/s) when i cranked things up a bit. Propeller flex was the biggest limiter I was encountering besides trying to keep in aimed in a mannor to keep water in the tank. The amount of energy it was useing was very minimal for the amount of flow it was provideing.
And yeah, that sort of circulation device would have the same sorts of bennifits of the vortech with the motor's heat being outside the tank and yadda yadda...
A few of you guys allready know, but I threw together a couple monster sized propeller powerheads magnetically coupled to the outside of the tank just for experiments. One with a 10" wooden RC plane prop, which required a 12" acrilic disk with 8 very strong neodimium magnets to keep things coupled to the motor on the outside. Basically pointless for normal sized aquarium circulation needs, as I just ended up makeing a huge mess consisting of at least a 3rd of the poor 55gal frag tanks water being on the floor, and many frags torn and floating around. I might mention that the drive motor I was useing for this experiment was the dewalt 1.2hp diegrinder I use for porting cylinder heads... The power limiter was the mag coupeling.
Anyways... I'm not interested in pump GPH anymore. Its about turbulance, and its about constructive flow patterns. I'm in the process of moving to tacoma right now, and when I get settled in, I will invite Don over to check out the newest innovation that my 90 will be useing. I'm not going to give the idea away yet (though Mojo helped me think of it on the phone), but its something I've never seen anyone else use. And of course it maintains my key design features of low power consumption, minimal water heating, minimal space in tank wasted, maximum flow, and no need to turn a nice tank into swiss-cheese.
Anyways, for something you can throw together in a couple hours on a weekend, 4 MJ900s modded properly and the cheapest ebay wave controler you can find will result in exellent flow properties for minimal cost, with minimal downsides.
