Circulation questions

[asylumdown]

So I finally got rid of my morbidly over-powered MP60s that couldn't be run any higher than 45% because of my stupid, stupid internal overflows (any more than that and they'd suck equal parts sand from the sand bed and air from the surface) and replaced them with MP40s. I now have 4 pumps that can all run at the same max speed, so I can finally start playing around with really cool flow programs through my apex.

Now, my first question is whether or not it's better to create a circular gyre that changes direction a couple of times a day, or try to create completely random flow? My problem is that with all MP40s, something like reef crest setting never runs the pumps at a high enough intensity long enough for eddies and currents to really reach the dead centre of my 6'X3' tank, but if I have two pumps diagonally opposite each other run at 100% while the other two run at no higher than feed mode speed, i can create a pretty respectable gyre that I can reverse. This brings much more flow to the centre of the tank. However, if I have the diagonal pumps at 100% and the other two diagonal pumps at say 40% the gyre completely falls apart, so I think I'd have to program it myself using short transitions and constant speed profiles instead of using a preset tidal swell mode or something. I'm just not sure which is better for coral growth.

My second question is how far I can throttle my return pump outlet. I've got a Reeflo dart which pushes approximately 3000GPH unrestricted, and with my unidirectional outlets that blasts the other side of the tank and has caused all sorts of weird and annoying coral growth patterns. It also totally overpowers any gyre the vortech's might make. I want to throttle it back quite a bit (I have a gate valve on the return line between the pump and the outlet in the tank) but I'm not sure if that will damage the pump, or what it will do to my energy consumption.

[IanWR]

Oh to have the dilemma of managing flow in a big tank.

I can't really help you with #1, but as to #2 it is my understanding that you can safely restrict the flow out of pumps. It apparently also makes them more efficient so you save a bit on energy consumption.

- Ian

[asylumdown]

oh that's great news! Might even help me with the micro bubble problem I've been having

[MitchM]

Your main goal should be to use the circulation to massage the SPS tissue equally which helps them to process waste and not cause one side to atrophy. If you can manage a higher flow rate in the upper level and a lower flow rate in the lower level for your LPS, all your corals should be happy with that.
A reversing gyre over a few hours should work ok, as long as you aren't blasting the direction with excess flow.
I agree with IanWR with the Reeflo, if you restrict the output you will save a bit on energy.

Your tank's looking great, btw.

[asylumdown]

Yah Iv'e come to the conclusion that my tank is just not set up right for a gyre tank. To create even the weakest gyre I have to run the pumps at 100% for an extended period, which would deflesh my LPS if I left it like that for too long. I could probably re-arrange my rock work to make it more efficient, but I'm not changing my whole tank now.