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Murray Hallam discusses his retrofit in the latest

Aquaponics For Profit

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NTF is a good growing system and I have used it in one of my systems for a while. It is light weight, and needs a support system to elevate to a good working level.  The holes in the channels are at set intervals. Depending on the length of the channels it may not be realistic to move them apart to allow more growing space as the plants grow. Good filteration is essential in NTF. The roots can get gunked up very quickly and go anaerobic without proper filtration. Once plants are in the channels and the roots have begun the intermingle there of no chance of moving them without root damage. NTF will allow water to heat up during the heat of the day due to the thin layers of water running down the channels. What most people don't think about is that the opposite will happen at night. The water can cool off substantially at night the same as warming during the day. If your area has cold nights the ambient water temps can drop very low at night and high during the day.

The raft method is also a good growing system as well and my systems all have raft components to them. There is no point in elevating the troughs(unless you want to triple the cost of the system instillation) when rafts of mature plants can simply be listed out of the trough and be easily brought into the shade for processing at a good working height. Water weighs about 8 lbs a gallon. On a standard 4 foot wide by 1 foot deep trough there is 240 pounds of water per lineal foot. Multiple 240 lbs x the length of the troughs and you know the weight of the system. To elevate all that weight doesn't make sense when rafts are light and easily mobile. I believe troughs are better left on the ground. I do have to bend over to pick up or drop off rafts, but the rest of the work is done in the shade next the stereo. The large volume of water stays at a very stable temperature and holds lots of DO. Yes there is larger air pumping requirements, but the air pumps and blowers are very efficient now. The power consumption is easily compensated by the rapid growth attained by ample aeration. I have recently diverted most if my aeration into my troughs instead of the fish tank. I get better growth with bubblers in the troughs and the fish still have plenty of DO to be happy. The raft method is a completely mobile system. My plants never stop moving until they get to the harvesting end of my troughs, then I move them out for sale. I start plants at a two inch spacing them spread them out to 6 inches for grow out. Since the roots dangle into water it is very easy to move then around with no root damage or stress to the plants. All this work is done in the shade at a good working height. Picking up rafts out of the water for maintenance does NOT cause stress or damage unless you let the roots dry out or expose them to excessive sun light. I have a working trough in the shade at counter height for doing all my work. I float rafts in the working trough when I am working on them to keep the roots happy. When I harvest a raft I replant it with the small plants in the 2" spaced rafts. I plant seeds, spread out plants, and harvest plants every week. This is the most efficient way of growing I have come up with and I am always improving on the efficiency.



Chris Smith said:

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'

 

Good concise summary on DWC/NFT Chris.
It is.  Thanks Chris :)
Chris: I agree with all you said but would like to add a footnote on the elevation issue.  In your setting, the soil temperature during winter months probably does not mess with your system's temp too much.  In temperate environments such as where I am, winter soil temperatures can easily stay at single digits (Celcius) for days on end and hit freeze point at night.  At those temps, having the beds insulated and a little off the ground does have some advantages.  Initial Cap Ex in lay-out is not so bad in comparison with a couple of seasons' constant heating.  You also do not have termites.................

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