how many bullhead catfish in a 175-200 gallon tank?

[Matthew]

Was hoping to buy (40) 1-2" and (10) 3".

 

I assume it can handle 50 fish at full size as I read of people using 55 gallon drums and having like 40 in them.

 

Will be filtering ~ 600gph

[TCLynx]

don't believe everything you read.  And don't expect to stock a brand new system with the max stocking density of fish right from the beginning.  Remember that a system needs to cycle up before it can support a heavy fish load. 

For my 300 gallon tank I would probably only stock it with 30 fish for grow out (of course I am growing channel catfish that tend to get several times larger than bullhead)  I have 600 gallons of gravel flooding and draining for that system and I'm pumping about 800 gallons per hour once ya figure in head height and plumbing and my timer.

 

Anyway I know there are people out there who say they go like 1 fish per gallon or 1 fish per 2.5 gallons but that is usually not very reasonable for a home aquaponics system unless you are talking fish that don't get big.  You also need to make sure you have enough filtration for the fish load.  How will you be filtering your 600 gph?

 

If you have at least 200 gallons of media or appropriate bio filtration for 20 lb of fish....

If you cycle up fishlessly first, then I could see you getting like 15-20 fish for your first batch.  If your first season goes well and you decide you want more fish in the future, then once you have the experience you will be able to judge if more fish will be appropriate for you to raise in that system. 

[Matthew]

I assumed some of the gravel and grow binds would do soem filtering (~40 gallons).  I have a 35 gallon bin which I modified with a huge like of green scrubbers from the dollar store(12 packs). I based it on a homemade bio filter design I saw on youtube but made it much larger.  Images below.

 

Also have Duckweed on the way from Ebay which I thought helped clean the water a bit and work as some food.  Was hoping their primary food would be night crawlers and redworms which I was going to breed in a barrel.  SOme guy on google claims to have only fed the bullheads that and they grew fine to maturity.

 

Really wanted to start out with the max fish because the only hatchery close to me is 1.5 hrs away and I only wanted to go there once.  Also was thinking of eating a few prior to full size. 

 

Was hoping the fish would breed the following year..

 

Dabbling with the idea of ptting a 55 gal drum sideways next to the tank to add more space.  Just would have it slightly higher than the current tank and let gravity do the work like with the grow bins.

 

Pads go on the  metal hardware cloth.  Then another hardware cloth on top of them to keep them in place.  Water pipe puts water under them and it flows up through them.

[TCLynx]

what is the metal hardware cloth made of?  generally galvanized metal is a bad idea for fish systems since the zinc can become toxic to fish.

 

I definitely don't recommend going with the "MAX" fish load to start.  How many gallons of gravel and gallons of scrubbies?

 

The danger here is if you overload your system, you could wind up killing all the fish and still need to make another trip to the hatchery once you are ready to re-stock.

 

A good starting stocking recommendation for flood and drain media systems is to have 1 cubic foot of media (7.5 gallons) per fish that you intend to grow out to 1 lb.  The scrubbies will provide more surface area for bacteria (several times greater than the gravel) but will only be effective if there is ample dissolved oxygen in the water of that bio-filter for them to work.  However, that bin won't provide any plant space for nitrate removal.  Duckweed can take up a good bit of ammonia but if the water level in your fish tank fluctuates or if you have any water splashing or bubbling alot of it will wind up stuck and drying on the sides of the fish tank above the water line and then when it gets back into the water in a dead form it will add to the bio-load while it decomposes and it will actually hurt your water quality in that state more than the living stuff can make up for.  So Duckweed probably needs to be in a separate tank with very gentle water flow for it to be of much help to you.