Hello again,
My forage raising tanks are almost complete. For now I have 3 100 gallon rubbermaid tubs that are connected to 1 55 gallon drum filter. Each tank has 2 two inch shower drains in the bottom and the entire outflow line to the filter is two inches. I have a ball valve for each tank so I can adjust flow or just shut one off if I need to. My inflow line on the top side of the barrel is one inch. So the water drains from the tanks into the bottom of the filter, flows up through the filter and I plan to have a pump to pump the water out through the one inch line back into the tanks. All of the tanks are at the same level except the filter that sits on the ground to allow a higher water level in the filter. My question is what size pump should I use to pump the water back into the tanks? Home Depot sells a 350 GPH Flo Tec pump for 88 dollars ,but I don't know if that's over kill or not enough. Please advise. Oh yeah, I plan to raise tilapia in 2 of the tanks and P.Kadiakensis shrimp in the other. I am going to cover the shower drains with gravel in the shrimp tank and probably turn the ball valve down to have a very slow drain in that tank. It's not complete yet so any ideas are appreciated. Thanks, John

I think the gravel and slow drain in the shrimp tank is a very good idea... If the shrimp spawn, their larvae are very small and don't have much swimming power, they'd be sucked and filtered away. Make sure you have some good rotting leaf/vegetative matter in the shrimp tank for the adult shrimp to feed on and for a healthy zooplankton population to form for the larvae to feed on. That is the biggest challenge of raising PK shrimp in tanks and aquariums, getting their larvae to survive...

John:

My gut feeling says that pump is more than adequate, but I'd look on an aquarium site or a RAS site to see if a total water change per hour is suitable. You'd be running slightly more than the total aquaculture volume thru the system every hour with that pump running full bore. You might be able to turn down the outflow on the pump with a bypass valve.

JohnK, sounds like you have a neat setup, I think you might want a water exchange rate of at least 2 or 3 times an hour. My 100 gal tank for PS's uses a 300 gph pump to the biological filter and works great, they are fed heavily but the ammonia and nitrite levels are zero.
Here's a pump that might work well.
http://www.harborfreight.com/cpi/ctaf/displayitem.taf?Itemnumber=66514

This is actually a very difficult question to answer. And the amount of info needed and equations one would have to run is, well, quite... on the side of head hurt.

That said, assuming you did a bit of research, and have an adequate solids filter and bio-filter. I would suggest at a minimum of four exchanges of water per hour.

Remember... You can pump all the water you want, and without reasonable filtration, it won't matter.

Sorry about that, I hope it didn't sound mean.

The shower drains work really well (I posted this type of info on another DG) 2" PVC is a definite plus. What I did is replaced the ss stamped grate with a ss filter screen. First ones were too fine, but anything like the size mesh of a window screen works. Keep in mind that they have to be cleaned on a regular basis, and a garden hose with an appropriate nozzle works on the larger mesh -vs- a pressure washer on the finer, but that is another story.

If there is a bait fish afterlife, I am sure to be on the list of those seeking revenge.

JKB...How's your Dad? Is he knitting you any stocking caps or making jigs while confined to the chair? I hope he's on the mend!

John, get yourself a good water test kit and keep an eye on PH, Ammonia,and Nitrites, if your water has low alkalinity and the PH drops you can add small amounts of baking soda to keep the PH in the range required.

Dad is doing fine! Thanks for asking! I feel like a pantywaist right now. He has more stuff broken, and at 81, he was plaining off Cherry Planks for a New Desk for my Mom for Mothers Day this week while hobbling around. He builds some really nice stuff.

All the breaks and splits are healing, slow, but solid. Put's me to shame! And He just goes with the flow!

That's a cool lookin pump at harbor freight ,but I am looking to use an external pump, not submersible. Sounds like there is a large range of opinions on the matter of the pump. Please contine to give your opinions as I haven't chosen the pump yet.

Well two of the three tanks are ready for fish. I am just waiting on my pump to be delivered. I ordered the 350 gph pump off e-bay for half the price of home depot. I hope it works I can't wait to get started.

So did you get these finished and are they working out for you. Please post some pictures if you can.

I am still in the process of trying to figure out which way I want to go. I think I will start with a few Aquariums and then move to the stock tanks.

Any thoughts.