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drdreww
05-12-2011, 08:59 AM
Hey so as I am building my first systemi know that it will be largely trial and error. But with 250g ft 55g sump and 60 cubic feet of grow space. What kind of extra oxegenation will I need?

rfeiller
05-12-2011, 09:45 AM
Urbanfarmer has been doing a lot of research on this topic.

urbanfarmer
05-12-2011, 11:25 AM
Oh boy... put me on the spot why dontcha... well, this is a complex issue with no "1 answer fits all" type thing, but...

First off, what kind of grow bed do you have for that 60 cubic feet? Is it gravel-type, floating raft, or NFT?

What kind of fish and how many fish are you planning to stock in the system? Fox example, Tilapia in a low stocking density may not need any added aeration at all with an adequate pump in a flood/drain system.

At a minimum, always maximize your aeration from the RETURN WATER FLOW. Let gravity pull it back to the FT, but try to add ways to split the water into as many streams as possible. This costs NOTHING and can be more than enough added aeration/oxygen to your system.

Hope that wasn't overly complicated and still helpful... we can tackle your exact issues with more information.

drdreww
05-12-2011, 11:43 AM
we are using gravel, 3/8 - 3/4 river rock probably (going to look at it today). we are going to start the system with perch, and move into Tilapia. wanting to get up around 50 - 60 lbs stock.

and thats great info about directing the return into multiple streams.

i hope to get a DO meter, but dont know when that will happen.

urbanfarmer
05-12-2011, 11:53 AM
I haven't read any literature on yellow perch, but assuming you are planning to grow them out to 50 lbs from something small, you can start without adding any aeration equipment. The flood/drain grow bed adds a lot of oxygen, which is why I asked what type. This is good. I would try it without and special aeration equipment like bubblers and just see how they react from week to week to the conditions they are in. The most critical times will be towards the end of their grow-out period and the few hours after you feed them.

Also, the more surface area you get on the fish tank where the water touches the air, the better, but I don't know if you have the option to change that in your design.

drdreww
05-12-2011, 12:04 PM
i dont have the option right now, because i am using a 250gal IBC for the tank. but i could add another tank later with water exchange only

urbanfarmer
05-12-2011, 12:07 PM
i dont have the option right now, because i am using a 250gal IBC for the tank. but i could add another tank later with water exchange only
Or split your fish into 2 harvests. This will lower the stocking density and increase the amount of oxygenated water to fish ratio. I think that's a good way to go.

keith_r
05-12-2011, 12:18 PM
perch do ok in low DO from studies i've read - actually better than bluegill,, that being said, i would an an aerator myself.. i think a pump for a 100 gallon tank will have 4 outlets, and probably under 60 watts, but would have to double check those numbers..
while many species can "tolerate" low DO, it doesn't mean you'll get the best growth from them..having an aerator on a battery backup is a good way to make sure at least some o2 is getting into the water in the event of a power failure

cedarswamp
05-12-2011, 12:31 PM
I've got an old whisper 1000 air pump that will easily do 4 12" stones on 6 watts of power. Cheap insurance IMHO.

drdreww
05-12-2011, 01:04 PM
Also what is the minimum reccomended size for the holes I drill in my PVC to distribute thewater in my GB

keith_r
05-12-2011, 01:12 PM
drilled holes have a tendency to plug, i have a tee with an outlet at each end of the gb, a valve can be used to adjust flow, but make sure you don't put to much back pressure on a pump or it will shorten the life of it..

urbanfarmer
05-12-2011, 10:31 PM
Ultimately, you can't put too much oxygen in the water, but you can put too little.

drdreww
05-12-2011, 11:24 PM
ok! thanks for all the replies guys. i will return multiple streams back into the tank, maximize surface area, and see how it goes!