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Murray Hallam discusses his retrofit in the latest

Aquaponics For Profit

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I have done cage culture of fish before. This was mainly to keep my tilapia from breeding uncontrolled in a mixed gender situation. Biggest challenge with cage culture is the feeding and making sure aeration and circulation are still adequate while keeping the feed from where the fish can't get it.

Keeping the tailapia in the cage and some catfish outside to eat the escaped food seemed to work ok but the catfish outside the cage were impossible to catch until after all the tilapia were removed and the cage removed.

I didn't like keeping the catfish in a cage since they seemed more prone to scraping themselves on it and getting sick but perhaps a different kind of netting would have been better suited to the catfish that what I used.

Your feeding "station" will probably take a bit of trial and error. I've found that tialpia and catfish are pretty good at splashing the feed out of any little feeding ring I've tried and even if you manage to avoid the splashing problem, many fish will take a mount full and carry it away only to spit it out cause it hasn't softened up enough for them to swallow yet. This seemed more prevalent with the tilapia I had than with the catfish.

Now I've often started seeds in my cups suspended above a tank using the wicks and I've seen Cosmo start seeds in floating seedling trays on his fish tank. Perhaps the happy medium might be to start the seeds over a raceway to provide some shading to the fish while not having lots of roots to be disturbed by or gunked up, then as the seeds grow and need more space, they would move to the shallower wider spacing of a standard raft bed set up? This sort of thing might reduce many of the drawbacks you are looking at while providing some of the benefits you are looking for.
I was wondering if the mosquito fish will eat the tilapia fry?
I dropped a couple of mosquito fish in my golden tilapia tank which Im trying to breed and after about 3 months I don't see any baby tilapias, only tons of mosquito fish?
mahalo
Larger tilapia fry and fingerlings will also eat the smaller ones too so between the older fry and the mosquito fish, the smaller fry probably didn't have a chance.
I remember when the FL group toured Morning star...they had an area netted off, in the holding tanks, for the fry to swim into for safety. Might save some, that way....at least the smart ones :-)
I think this topic is an interesting one to look into.  Is NFT or DWC more efficient for commercial AP and small scale too.  They both have their pros and cons. Im interested to hear from people who have tried both styles about what their experiences were.

Well on a materials stand point I expect the DWC could really have benefits to a large scale operation where it is simply a really big raft tank covering the whole floor of a high tunnel.  However in real life logistics this may not be as reasonable.

 

NFT will have a far lower total volume of water but require the troughs and supports and finer filtration before the water goes to the plants.

 

Between the two, the structure to put NFT above the fish tanks will be more reasonable but separate bio-filtration is required and water temperatures will fluctuate more in the NFT.

 

Ya know, it is really going to depend on the situation to figure out which is more efficient.  I expect roof top greenhouses will go for the NFT since weight and space are premium and more climate control is probably already called for.  In a spacious out door on the ground situation, rafts may be more appropriate as long as leaves and debris blowing into the raft tanks can be controlled.

NFT =  more materials and more maintenance for same space as well as additional heating\cooling costs.  That's what I got out of watching Murray's video in the above link.

Good points TC. 

I have been leaning towards DWC for ease and NFT for efficiency. They both seem awesome, but im really just gonna have to try them out. These are just some things i have thought of off the top of my head...

NFT: PROS: Light weight, can vertical garden with these, lower NRG usage because not much extra aeration is needed in comparison to DWC, can move channels close together when plants r small then slide the channels further apart as plants age increasing space efficiency, theoretically since NFT uses about 1/4 the water of DWC you could grow 4 times the amount of plants with the same amount of fish because dilution of nutrients would be much less

NFT: CONS: Filtration must be top notch, H2O temp changes faster, less water than DWC making it less stable

 

DWC: PROS: Lots of H2O, could be cheaper to build, more stable,

DWC: CONS: A lot of weight to support, alot of air pumps must be integrated into the system to match oxygen levels of NFT, filtration must be good, set plant spacing in rafts causing a loss in space efficiency, must bend over more to inspect plants without causing stress (removing the raft w/ plants in it and putting it back into the trough for maintenance will definitely cause stress to the plants; this would make multiple harvests more work.  also if your are not able to do more than 1 harvest your will have to buy more seeds, and it can longer to start a whole plant over rather than get multiple harvests due to the plants structure being intact)

 

Just some ideas for brain stormin'

 

The system I'm thinking of will be a combination of gravel, deep water culture, and NFT. The reason being to keep the water clean for the fish and the fact that different plant types are possible. So to answer the question, yes!
My current commercial design is a combination, because I do not think that any one system is best as a single unit.  Gravel beds allow for maximum nutrient retention and simplified filtration.  Rafts are probably the most productive leavy green method available, and vertical towers allow you to exploit the space left above the rafts.  The fish tanks and gravel beds will occupy around 30% of the system footprint, with the rafts and towers getting the bulk of the floor space.
AJ, are you experienced at the growing methods that you are comparing or regurgitating information you have read? I do not agree with some of your comparisons and I think they are misleading.

AJ Grottke said:

Good points TC. 

I have been leaning towards DWC for ease and NFT for efficiency. They both seem awesome, but im really just gonna have to try them out. These are just some things i have thought of off the top of my head...

NFT: PROS: Light weight, can vertical garden with these, lower NRG usage because not much extra aeration is needed in comparison to DWC, can move channels close together when plants r small then slide the channels further apart as plants age increasing space efficiency, theoretically since NFT uses about 1/4 the water of DWC you could grow 4 times the amount of plants with the same amount of fish because dilution of nutrients would be much less

NFT: CONS: Filtration must be top notch, H2O temp changes faster, less water than DWC making it less stable

 

DWC: PROS: Lots of H2O, could be cheaper to build, more stable,

DWC: CONS: A lot of weight to support, alot of air pumps must be integrated into the system to match oxygen levels of NFT, filtration must be good, set plant spacing in rafts causing a loss in space efficiency, must bend over more to inspect plants without causing stress (removing the raft w/ plants in it and putting it back into the trough for maintenance will definitely cause stress to the plants; this would make multiple harvests more work.  also if your are not able to do more than 1 harvest your will have to buy more seeds, and it can longer to start a whole plant over rather than get multiple harvests due to the plants structure being intact)

 

Just some ideas for brain stormin'

 

Thanks for hopin in to this discussion Chris, your raft systems look amazing!  I was just brainstorming before i make investments; trying to get the most bang for my buck (it would be extremely stupid to not research something before you invest).  Let me know what you think is misleading b/c u obviously have alot of experience with rafts, id love to hear what you've learned from your experiences (also NFT if you have done it before).  Im not trying to lead or mislead anyone, they are just simple brainstorm ideas; as i stated clearly in my post.  If anyone solely believe what one person says anyways, they need to broaden their horizons. i was merely trying to create a discussion.  I also want other peoples opinions/experiences to help mold my own, or else i wouldn't have put them up in a forum lol. Please, i want to hear other peoples ideas; I also believe each person has different need/wants in a system, so what might be right for someone but be completely off for the next.  Chris, can you elaborate on how u integrate your ebb+flow bed into your raft systems, because that seems like a real winner in my eyes.

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