Backyard Aquaponics
A place to discuss aquaponics

so...um, I added the maxicrop and, wow...my water is quite dark...the fish will be okay? (I need some reassurance here...)

Yea they will be fine

One size of catfish, or mixed sizes?

I applied TCLynx's initial rule of thumb post to the grow bed I plan on using. Here's what I came up with:

500 gallons of grow bed
250 gallons fish tank
100 lbs of fish (absolute maximum grown out weight)

& if i want to go with a 15 minute fill / 45 minute drain cycle, I'll need a pump capable of pushing 17 gpm

Am I in the right neighborhood ?

Got to thinking about the question "mixed or same size catfish?" I put a dozen fingerling catfish in when I introduced fish and they are mostly 4-5 inches long and starting to get rather broad now. There are just seven of them left but I never saw any floaters so I have to think a couple of runts got eaten. Don't know for sure of course but what other explanation could there be? At some point I want to introduce some more, but this makes me not want to put new ones in without having them in a nursery of some sort or starting them over in the tank where I dechlorinate my top off water. Don't know that would be good for them though. The ones I have seem to be enough for the plants that I have now, although I do suppliment with a little maxi-crop.

Hey guys I am new to all of this looking to relocate to Wilmington
Anybody out there need a novice / assistant?
I am really interested in this
Pete

I would recommend actually fewer lb of fish now days at least for your first season, do like one lb fish for each 7.5 gallons of grow bed (so that would be 66 lb of fish) and I prefer to make sure each 1 lb fish has at least 5 gallons of fish tank (which would be only 50 lb of fish.)
Once you are an expert, you can adjust as needed but for as long as you have to ask "how many fish?" the answer is always less.

Also, if you are going to flood 500 gallons of grow bed and you only have 250 gallons of fish tank, you will also need a sump tank or some means to keep your fish from needing to learn to breath air when you flood your grow beds.

this is why so many people don't stop at just one system. When you are ready to get more fish it is good to quarantine them in a separate system at least for a time to make sure you don't bring in a disease or parasite into the existing population and it give you a "nursery tank" to keep the small ones in for a time as well.

That said, I'm not sure HOW likely the small catfish are to get eaten if you are feeding the bigs ones well. I noticed that my big catfish can be quite lazy and didn't do a good job of eating the tilapia fry/fingerlings but tilapia are really fast and catfish can be quite a bit slower.

Is there fish tank to sump tank ratio? I am lookin to setup a system using a 275gallon IBC and I am wondering if the sump tank should be equal to or a little smaller than the fish tank?

Not sure if this thread is still active. Are there any rules of thumb for grow towers?

I have a CHIFT PIST system with a 1000 litre IBC fish tank, a 1/3 IBC ebb & flood GB (~300 litres wet gravel) a 100 litre 1/2 barrel continuous flood GB, and 2/3 IBC ~600 litre sump tank part sunk into the ground. I will be adding 20 X 1 metre 90mm PVC pipe grow towers in stage 2. Water is pumped from ST to header pipe into the grow towers which trickle into a collection pipe which goes into the fish tank, which gravity feeds via SLO into the two grow beds, which flow back to the sump. Excess water not required for the towers is diverted from the header pipe to the collection pipe.

In my earlier research I found a figure of 1 x 5 foot grow tower for every 2-5 pounds of fish at maturity. I converted this to 0.5-1.5kg fish per metre of grow tower (from Bright Agrotech, I think).

Does this mean I can sensibly support 16 fish with my growbeds (25 litres of wet media per fish) and another 20-40 fish with the grow towers? If so, would a total of 30 trout fingerlings be okay for an immature system that has just cycled?

What about flow rates for grow towers. Again, my earlier research came up with ~40 litres per hour through each grow tower. Does this sound about right?

Max,

Especially if you are running a flood and drain. You want to size the ST to be able to hold the full amount of water that could drain out of your GBs if the power shut off.

Max, it is chalanging to over size your sump. The more volume, the better. like FloridaFishin said, it needs to be at least as large as the total bolume of all your flood and drain growbeds, but i like a little more volume so as not to need topups as often.

Thanks! I have 3 growbeds, about 100 gallons each. After being filled with media the capacity is probably about half that. My sump is 200 gallons and is working perfectly. You can see my build thread here:
viewtopic.php?f=18&t=24435

ONLY use that rule of thumb for amount of fish per grow tower IF you are using ZIPGROW towers!!!!! Those numbers DO NOT APPLY if you are using PVC pipe with water trickling down it with or without media. The ZIPGROW matrix media works well as filtration in a vertical trickle through design. Most other media winds up channeling the water and only a little of it gets wet and therefore you can't count on the volume of media filtering the same way as flood and drain or even constant flood gravel.

Figuring out how much fish mass your towers can filter for is likely to be trial and error so I wouldn't count on adding some particular number of fish because you put the towers online.

Thanks for the advice TCLynx. I have just hung my towers and have 6 filled with old bird netting and running. The finger test shows there is a fairly good distribution of water through the media, but I will take a very conservative approach with the numbers of fish. Will probably start with 20, which is only 4 extra fish for the 20 towers.

My next dilemma is the pump volume now that it is operating at the higher head for the grow towers. It is a 2000 L/hr pond pump that is pumping at ~700L/hr at 2 metres head (it was probably doing around 1000L/hr when short cutting directly to the fish tank). It is enough for the grow towers and the grow bed is now flooding and siphoning after some adjustment with a 7 minute fill and 2 minute empty (was filling in 4 1/2 minutes). However, I am concerned that it may not be sufficient flow for the system overall as the FT is ~1000L and the sumptank is ~5-600L, so the water is only completely circulating in just over 2 hours.

Options:
1 - see how it goes at 700L/hr
2 - get a bigger pump and have the 2000 as a spare (but it may be too much for the system to handle - would have to recirculate excess flow within the sump, and the 3000L/hr is 70w rather than the 45w for the 2000)
3 - get a smaller 1000L/hr pump (16w) and run it directly from the sump to the fish tank with a venturi to provide additional aeration as well as moving more water through the growbeds, and providing a margin of safety should one pump fail.
4 - do I need additional air pump with any of the above options?