Flow for a 320 Gallon Display Tank

Hello 3Reefers!
Now that my 320 stand is in the basement and my 320 gallon Great Lakes Aquarium is being built, I'm starting to think about the equipment.
Flow for this size tank is something new to me; I have accumulated some gadgets so far, but I'm not sure if it's enough.
First, the return pump is a Reeflo Gold Hammerhead/Barracuda.
Next, I have a Tunze 6215 Wavebox.
Finally, I have a 4-Return Oceans Motions Device.

The tank is going to be a peninsula tank with the overflow and wavebox on a short end. I will plumb the return into the Oceans Motions device, but I'm not sure where to put the 4 returns. I thought at first to plumb two of the returns down to the bottom of the tank and make a couple of runs along the bottom and hide them with rock and sand. The other two I was going to position at the short end opposite the wavebox. My concern of putting high flow at the bottom is I would end up blowing sand around and/or upsetting the LPS corals.
But I'm still not sure if this is enough flow...
I aspire to make this a predominantly SPS-filled tank but I do love some softies and LPS.

I think the Maxspect Gyre pumps are pretty cool; I thought of getting one to position at the short end of the tank...
Decisions, decisions...
Any advice would be appreciated!

 

I hear the Gyre is great for big tanks. There are a few people on here with ~300g who have gyres, hopefully they will chime in with more info on their experiences.

 

I would place the 4 OM outlets near the four upper corners. You do not want to place any return near the bottom or you run the risk of siphoning the entire tank out in a power outage. Never place a return any lower than you want to see the level of your display drop to when the power goes off. I have my OM Squirt two way nozzles in each upper back corner about 1.5" below the surface so the tank wil never backsiphon more than 3.5 gallons back to the sump when the return shuts off. I know I always have at least 8 or so gallons or freeboard or spare room in my sump so a flood is not an issue.

If you want them around the bottom you will need to plumb them in a closed loop configuration which would require an additional pump.

 

What about a check valve?

 

Check valves are a false sense of security and can and do fail. Remember, it does not have to be a catastropic failure, even a trickle will flood given a little time, and tha tis usually at night or when you are not home.
One speck of sand, some food, a small snail, a little algae that breaks away during cleaning, basically anything can defeat a check valve. The other thing is check valves add additional headloss to the return circuit and can even stick partially open or partially closed andcreate more issues. Its best to leave them out all together. A saltwater reef aquarium is basically a miniature wastewater treatment plant where you are processing ammonia to nitrites and nitrites to nitrates via the nitrogen cycle and removing organics via skimming etc. In the municipal wastewater industry we avoid check valves like the plague and depend on air gaps whenever and wherever possible as they cannot be defeated or fail, the simplest form of backflow prevention know to man and thye require zero maintenance or cleaning.

With a properly designed return and sump there should be need for things like check valves or drilled holes to act as siphone breaks which also plug and fail. Leave the returns close to the surface so only a small, very easily calculated amount of water backsiphons in a power outage before the return is exposed to atmosphere and you have an air gap. We all know water cannot jump uphill to the return nozzle once exposed so the siphon breaks and flow stops and a flood cannot happen.

 

Thanks for the reply! I was leaning toward the returns on the top anyway; I want to minimize the amount of visible equipment. I want to avoid things like VorTechs on the short end since the end opposite the overflow will be viewable. So do you think the OM 4-way and the Tunze Wavebox would be enough?

 

I have a 300DD and run 2) RW-20's and it's almost too much. My tank is six feet long. I think they would be perfect in a longer setup. My sand bed gets tossed around if I crank it up or take them off wave mode. I'm also thinking heavily on getting the Gyre for my system soon.