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| Water to plant ratio? http://byap.backyardmagazines.com/forum/viewtopic.php?f=12&t=5490 |
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| Author: | Bdub1286 [ May 19th, '09, 13:17 ] |
| Post subject: | Water to plant ratio? |
Ok, so I need a little help about water to plant ratios. I have seen a lot of information about water volume to media volume, but my system does not incorporate large grow beds like others do. What I have done is used two hot tub shells and buried them in the ground so they act as my fish ponds. I have a large amount of PVC in 4, 5, & 6 inch and decided I might as well use it. I was thinking about using 8-10 sticks of pipe for each hot tub. The sticks are 10 ft. long and will have holes drilled every 5 inches or so. Each one of the hot tubs holds about 400 gallons of water but I can fill it to whatever volume I need. I'm just not sure about the ratios because I will be using net pots with only small amounts of medium. I'm just wondering if there was anyone else that had a system like this or could help me out with the ratios? I would like to know how much fish I can safely stock in one of these hot tubs for the amount of plants I intend to grow in the PVC pipes. Thanks a lot everyone. |
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| Author: | Outbackozzie [ May 19th, '09, 13:22 ] |
| Post subject: | Re: Water to plant ratio? |
Small plants like letuce get away with a 5" x 5" root growing area, bigger stuff like tomatoes require feet of room. I have one bush that has totally filled (to blocking point) a 2' x 2' barrel. |
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| Author: | RupertofOZ [ May 19th, '09, 13:44 ] |
| Post subject: | Re: Water to plant ratio? |
Bdub1286 wrote: I'm just not sure about the ratios because I will be using net pots with only small amounts of medium. I'm just wondering if there was anyone else that had a system like this or could help me out with the ratios? I would like to know how much fish I can safely stock in one of these hot tubs for the amount of plants I intend to grow in the PVC pipes. Thanks a lot everyone. How many fish you can stock is directly related to how much filtration volume you have... Normally in media based flood & drain systems it is fairly easily calculated... and is suggested at 3kg/100L of fish tank volume... with an accompanying minimum growbed (filtration) volume at least equal to your tank volume... a 1:1 ratio As you only intend to utilise net pots filled with media.... then your actual filtration volume (and stocking density) ... is determined by the total capacity of the net pot media... Two other important consideration in such a design.... the volume of water that will be required for circulation through the pipes, in relation to the volume of your tank(s)... Ad the need for pre-filtering of solids before distribution to your pipes... this will result in an additional filtration capacity that will again affect your stocking density... in this case raising it, as compared to that of the media filled net pots alone... My suggestion would be to incorporate a flood and drain growbed before your NFT net pot pipes... failing that, you will need some sort of external filtration method... |
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| Author: | Bdub1286 [ May 19th, '09, 14:35 ] |
| Post subject: | Re: Water to plant ratio? |
I am not doing an NFT system. The first PVC pipe will be completely filled up with water which will then gravity feed down into the next pipe, and so on. I will actually only be using about 50 gallons of water at a time to complete this process. This is basically just a flood and drain type system except I am using PVC pipe and net pots instead of a grow bed. There will be solid filtration systems before and after the water enters into the PVC grow pipes. |
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| Author: | Outbackozzie [ May 19th, '09, 14:49 ] |
| Post subject: | Re: Water to plant ratio? |
Still sounds like NFT, especially with no media in the tubes. |
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| Author: | RupertofOZ [ May 19th, '09, 14:50 ] |
| Post subject: | Re: Water to plant ratio? |
Ok... so is the pipe fill a timer based pump arrangement?? How big are your pre & post filter growbeds? |
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| Author: | Bdub1286 [ May 19th, '09, 14:59 ] |
| Post subject: | Re: Water to plant ratio? |
The water will be pumped up to a holding tank which will drain once it gets up to a certain point. This water will flow into the first pipe and once it becomes completely full it will drain into the next pipe, and so on. This is not an NFT system, there is not constant flow of water through the pipes. They are filling up and then draining. Yes it will be used with a pump which will most likely be on a timer. I am using a solids filter at both ends, not another grow bed filter. Kinda like a simple screen which will make sure no large particles enter or exit the grow tubes. |
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| Author: | Sleepe [ May 19th, '09, 15:17 ] |
| Post subject: | Re: Water to plant ratio? |
One problem is the lack of biofiltration, the number of fish, or more accurately fishmass, is dependant on the ability to convert ammonia to nitrite to nitrate. The fish are dependant on this. Most use GB's to do the conversion but this is not strictly necessary, You could go from FT to screen to biofilter to your slightly unusual  F&D DeepwaterNFT tubes.
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| Author: | RupertofOZ [ May 19th, '09, 15:28 ] |
| Post subject: | Re: Water to plant ratio? |
While a screen will filter out most large solid particles... and may prevent most problems with solids attaching themselves to the root balls.... The screen itself wont provide much in the way of bio-filtration... nitrification, as Sleepe says... Leaving only the media filled net pots to do this vital function.... The number of pots and volume of media within them is "limited".... thus limiting your filtration capacity and stocking density... The question then is.... will you be able to stock enough fish to supply sufficient nutrients to/for your plants... 
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| Author: | Outbackozzie [ May 19th, '09, 16:25 ] |
| Post subject: | Re: Water to plant ratio? |
Mesh aint enough Bdub. |
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| Author: | Bdub1286 [ May 20th, '09, 02:09 ] |
| Post subject: | Re: Water to plant ratio? |
So basically what your saying is that you don't think I will have enough medium for the bacteria to grow in for the nitrification process? Wont the bacteria grow other places than just in the medium? What do you suggest that I do to filter the ammonia? |
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| Author: | Angie [ May 20th, '09, 03:21 ] |
| Post subject: | Re: Water to plant ratio? |
The bacteria will grow on everything that they have available so whatever your current filtration is, you can safely add an additional 10% buffer for what is known as passive filtration- bacteria on the inside of piping, pumps, underside of rafts, etc. This is the general scientific census on biofiltration for flood and drain and raft style systems. Available on line- Recirculating Aquaculture Tank ProductionSystems: Aquaponics—Integrating Fish andPlant Culture A volume ratio of 1 ft3 of fish-rearing tank to 2 ft3 of pea gravel hydroponic media (1⁄8 to 1⁄4 inch in diameter) is recommended for reciprocating (flood and drain) gravel aquaponic systems. This ratio requires that tilapia be raised to a final density of 0.5 pound/gallon and fed appropriately. With the recommended ratio, no solids are removed from the system. The hydroponic beds should be cultivated (stirred up) between crops and inoculated with red worms to help break down and assimilate the organic matter. With this system, nutrient supplementation may not be necessary. As a general guide for raft aquaponics, a ratio in the range of 60 to 100 g of fish feed/m2 of plant growing area per day should be used. Ratios within this range have been used successfully in the UVI system for the production of tilapia, lettuce, basil and several other plants. In the UVI system all solids are removed, with a residence time of <1 day for settleable solids (>100 micrometers) removed by a clarifier, and 3 to 7 days for suspended solids removed by an orchard netting filter. Another factor to consider in determining the optimum feeding rate ratio is the total water volume of the system, which affects nutrient concentrations. In raft hydroponics, approximately 75 percent of the system water volume is in the hydroponic component, whereas gravel beds and NFT troughs contain minor amounts of system water. Theoretically, in systems producing the same quantity of fish and plants, a daily feeding rate of 100 g/m2 would produce total nutrient concentrations nearly four times higher in gravel and NFT systems (e.g., 1,600 mg/L) than in raft systems (e.g., 400 mg/L), but total nutrient mass in the systems would be the same. There is a lot of good information in this booklet- if you can get past some of the technical terms and math, for some that might confuse them more. |
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| Author: | Sleepe [ May 20th, '09, 07:04 ] |
| Post subject: | Re: Water to plant ratio? |
So basically what your saying is that you don't think I will have enough medium for the bacteria to grow in for the nitrification process? Wont the bacteria grow other places than just in the medium? What do you suggest that I do to filter the ammonia? Its not so much that they won't grow elsewhere its just that there is unlikely to be sufficient surface area to handle very many fish. If you don't wish to go down the large volume media gb's the easiest is to install a biofilter. With the system you intend to employ you need firstly to remove the larger solids ie mechanical filter then through your pipes and into a biofilter then to the FT's. The biofilter could be as simple as a plastic barrel filled with bioballs, cut agcoil or coarse foam etc. You can either inlet at the bottom and overflow the top or inlet the top and outlet the bottom. The first tends to give you a little saftey margin if the pump etc fails, the media will not dry out however it is only temporary as the bacteria are aerobic ie they require oxygen and it should have a tap on the bottom to occasionaly empty out crap. The amount of fish you wish to stock is then mainly dependant on the efficiency of your biofilter and its media surface area. I was not trying to knock your proposed system as new ideas are always interesting
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| Author: | Jensilaedi [ May 21st, '09, 10:28 ] |
| Post subject: | Re: Water to plant ratio? |
I was also trying this idea as well but I also quickly found out that I'd need a biofilter. So after a long deliberation I decided to have real GB containers. Its less hassle and I wouldn't need a whole lot of fittings and plumbing as you would need to do if you were going with a biofilter plus Flood and Drain Pipes... I was thinking ... fish tank "CHIFT" and then from that little sump next to the FT will be a pump up to the top big pipe and flood and drain to the next pipe, a lot similar to yours but as I said, I'd have to turn the little sump into a biofilter for better success. My newest big system is based off this idea, except I'm starting with big container beds first and later when the system has cycled I'll add the pipes and do it like you're saying, Bdub. And you're not the first person to try this Flood and Drain in deep pipes idea out... so don't be put out, it's not a bad idea, in fact its a great idea that lots of people have already tried it. And they all have found that they need lots of surface area for the nitrification process to equalize the ammonia input by the fish and enough food for the plants. 
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| Author: | TCLynx [ May 21st, '09, 22:54 ] |
| Post subject: | Re: Water to plant ratio? |
The media filled flood and drain grow beds serve multiple purposes all in one package. 1-Solids filter (that doesn't need constant cleaning or replacing) 2-Bio Filter (that doesn't need extra aeration added) 3-Plant growing space with support for large plants 4-composting worms can help out with it all It isn't that you idea can't work, you just need to add a few items to your idea to make it function. You need quite a lot of solids filtration (a simple screen or sponge will likely need daily attention as they clog quickly once a system is cycled.) You will also need a bio-filter of some sort, a barrel full of bio balls or something might handle things but you need to make sure it gets enough aeration as well as flow thorough to do it's job well. There are many bio-filter ideas out there so do some searching for what will work for you. Something to keep in mind about plants growing in pipes, the roots tend to get big and clog pipes so regular root pruning may become necessary for some types of plants. Also, most plants growing in net pots in pipes get a constant small flow in the bottom of the pipe, This allows for air to get to the roots but the constant flow keeps the plants from drying out. If you will be doing intermittent flow yet keeping the pipes full, you will probably find added aeration is needed for the water in the pipes to keep the plants in good health. If the pipes will be empty between pump cycles, then you plants will suffer from drying out on hot/dry days. That is the problem with NFT, if something fails, the plants not getting water suffer pretty quickly. In DWC you want to make sure the water has plenty of aeration as water low in dissolved Oxygen can cause many plants to languish. I'm not quite sure how your media-less pipes will do for flood and drain so if you do take on the challenge, please Run a system thread to show us your results and how you deal with the different special challenges. |
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