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PostPosted: Jul 21st, '21, 17:07 
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I have an old AP system that I made by cutting the top off of an IBC tote, flipping it over and rotating 90°. It was flood and drain, using a timer for the pump. I used sand as a medium to keep costs down. (I hadn't heard of IAVS, so I didn't get it quite right.) It worked and got better for three or four years. Then the top became so deformed under the weight that the water ran over the side of the GB, rather than through it. It didn't get used last year.

I saved my surviving fish and the (already cycled) water. I've added a second tank and plan to add a third. Tank one has feeder goldfish, tank two has a few koi. Tank three is for duckweed and what we call crawdads. (I think for most members they're "yabbies".) Tanks are connected via siphon bridge made of two inch PVC. I have one pump, pumping from tank one to tank two.

My first instinct was to make the same kind of sand GB, but better supported. But I'm afraid of it failing again. Maybe I should try something new. I have some four inch PVC and fittings, and I'm thinking of an NFT system, but it's well outside my knowledge base. Do NFTs need to run constantly? How large should I drill the holes? How far apart? Will I need net cups? Can I cap the four inch pieces, then connect them in rows using smaller pipe and uniseals? (As opposed to connecting the paralell rows with pairs of four inch elbows, with more pipe in between.) How large would my smaller pipe need to be so I wouldn't overfill the first pipe faster than the water could level across all of them? I'm sure I'm not giving you all the info you need to help me. Let me know what you need. Also, I'll post pictures tommorrow if it helps.

I think the best thing about my old GB was filling the pores of the sand first with water, then with air. Biological filtration. Could I build another PVC GB, like the NFT, but with sand inside and get the same effect? If so, how would I keep the sand in the four inch pipe and out of the smaller pipe that drains back to the fish tank?

If you've read this far, thank you. And thanks in advance for whatever advice I get.

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PostPosted: Jul 24th, '21, 10:36 
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Even though I'm still deciding what to do for my grow beds, it's high time I start getting some plants in the system. (Besides algae.) So I bought some insulation board yesterday, took a guess about how big to cut it, and today I started drilling them to use as rafts. My first DWC. For now I'm using the circles I cut out as plugs/ cutting holders. They fit a little too loose. So far I've put in cuttings of rose, tomato, comfrey, lamb's quarter, bamboo and the last piece of pothos my mother-in-law's cats failed to kill. Only the pothos has any roots so far. (I've been working with it for a whole now.

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PostPosted: Jul 24th, '21, 10:49 
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And here's the pictures I should've including with my first post:

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PostPosted: Jul 26th, '21, 22:12 
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NFT requires very good solids filtration or the plant roots get coated with solids and the plants do not grow well, or die. Also there are those that will argue that if the tubes are not square then it is not NFT. But that's another argument.

I sometimes use 4" round tubes in addition to my grow beds. I have an RFF solids separator before the grow beds and I use post-grow bed water AND run it through a secondary solids filter before using it for the NFT tubes.

I have caps on the end of the 4" tubes and my inlet / outlet water are 3/4 PVC. It works pretty well. I use 3" net pots and I think I drilled holes every 12", though when plants are doing well this seems too close together as I can get large root masses that extend more than 12".

I also find it difficult to start plants for NFT. I don't know how it is supposed to be done, but I start mine in 3" net pots in a raft bed to get some roots long enough to reach the water, then transfer them to the tubes.

It's a fair bit of work so I do not use them often. When I do it was mostly for smaller or leafy plants like spinach, lettuce, strawberries, etc.

If you don't have a robust solids separation, bio-filter and water polishing then I would avoid NFT. You already have experience with sand beds and they perform best without solids filtration. It sounds like you just need better support for your grow beds and a timer for the pump to make it an IAVS type system.

I also strongly recommend a sump tank, make stands for your grow beds to lower them, and use a solids lift overflow (SLO) from your fish tank. So you will have what's called a chift-pist system, constant height in fish tank, pump in sump tank. Water overflows from the fish tank to supply the grow beds. The water drains from the grow beds to the sump. A single pump moves clean water from the sump back to the fish tank. No solids filter needed for sand beds, pump floods sand beds for 15 minutes once every two hours. I use a smart wifi outlet for a timer as I can program anything I want for start / stop times. You want the fish tank volume and the grow bed volume to be at least equal, up to 1:2 FT gallons to GB gallons (wet media).

But that's just what I would do. Everyone has different solutions that best fit their situation.

BTW, raft beds need good aeration so you likely will have better success if you introduce an airstone.

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PostPosted: Jul 27th, '21, 03:57 
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Thank you. I think I am going to bring back a sandbed of some form. I liked the security of having a huge bio filter in the system. Besides which, the plants seemed to get better as the solids accumulated. (As you said, no pre-bed filter needed.)

As for my DWC, I'll have to hand pick plants that don't mind wet (anaerobic) feet, find a way to get some of the roots above water, (like in kratky) or get a decent air pump and some stones.

I currently have one pump, so my FTs kinda are like the sump you mentioned. Right now I'm running it all the time, with filter floss (quilt batting) on the intake for filtration. I'll have to choose between putting it on a timer or adding a second pump for GBs.

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PostPosted: Jul 27th, '21, 04:56 
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If you intend to do sandbeds/iAVs, you might want to consider learning about the way it works before throwing money at a system you don't fully understand. You can waste a lot of time and money if you don't have a good direction to be heading. I tried to help you a couple years ago on some other site when you did your first sandbed experiment that went sideways. Cruise around this site to get a better understanding of what I think you're trying to do..... https://garydonaldson.net/home/iavs/ If raft or nft is where you're heading, nevermind.


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PostPosted: Jul 27th, '21, 05:04 
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Actually, you did help me. (Thank you.) I was running it as constant flood, you convinced me to switch to ebb & flow. I also looked up IAVs, though I could use a refresher now. I just never rebuilt my system until now. If I use sand, I'll be revisiting the site and videos you showed me then.

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PostPosted: Jul 27th, '21, 16:14 
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Looks as though the primary shortcomings of my previous system vs iAVs are/were:

1) I put in a furrow around the sides in order to keep all my plants from washing out. In iAVs, there's a system of connected furrows to distribute water evenly while keeping plant crowns above the water line. I think this slows the flow compared to my old system, letting more water run through the sand instead of over it, thereby making it a better mechanical filter than my GB was.

2) I cobbled together a drain inside a pipe inside a bucket with gravel as a media excluder. ̶I̶n̶ ̶i̶A̶V̶s̶,̶ ̶i̶t̶ ̶s̶e̶e̶m̶s̶ ̶t̶o̶ ̶b̶e̶ ̶a̶ ̶s̶i̶m̶i̶l̶a̶r̶ ̶d̶r̶a̶i̶n̶,̶ ̶(̶v̶e̶r̶t̶i̶c̶a̶l̶ ̶p̶i̶p̶e̶,̶ ̶o̶p̶e̶n̶ ̶o̶n̶ ̶t̶o̶p̶ ̶f̶o̶r̶ ̶o̶v̶e̶r̶f̶l̶o̶w̶,̶ ̶h̶o̶l̶e̶ ̶d̶r̶i̶l̶l̶e̶d̶ ̶a̶t̶ ̶b̶o̶t̶t̶o̶m̶ ̶t̶o̶ ̶d̶r̶a̶i̶n̶,̶ ̶b̶u̶t̶ ̶s̶l̶o̶w̶e̶r̶ ̶t̶h̶a̶n̶ ̶t̶h̶e̶ ̶p̶u̶m̶p̶) but with a fabric sleeve media excluder.

-----EDIT----- Nope. Just saw the demo video. He drilled a series of holes and covered with cloth, then wet sand to hold it tight.-----


3) iAVs uses management practices to get the solids where they belong. (Sloped bottom fish tank, solids lift overflow (SLO).) I didn't have either of those. Still don't. I can research the SLO and probably build it, but how practical is it to tilt my IBCs? Or is the inbuilt slope enough, if I put the SLO in the depression behind the drain valve?

My iAVs research/ to do list (so far):
a. Research SLOs.
b. Research how water gets into the sand bed without disturbing the sand. In the demo video, it looked like he had a tee and a valve to divide the flow and adjust output speed.
c. Figure out fabric sleeve. (Geo-textile?)
d. Look up specs on pump. Now that I have more water, it's turnover rate is probably sub optimal.

My GENERAL research/ to do list (so far):
a. Patch hole in middle tank where bulkhead was.
b. Aerate roots in DWC.
c. Shorten existing siphon bridge and build second one.
d. Look into advantage of adding a sump.

I welcome any input and advice re: any of the above, but I'm not just dumping it off. It's my legwork to do, and I'll either do it or suffer the consequences of not doing it.

I will ask you folks, though, does it look as though I have a right understanding (so far) of iAVs?

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PostPosted: Jul 28th, '21, 03:06 
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If you plan to combine iavs with normal grow beds and nft, or otherwise need your pump to run continuous, you can add a timed valve to supply the sand bed(s). I think post-sand water will work well for nft without additional filtration, so maybe the sand bed drain feeds the tubes before returning water to the sump. Normal media beds may benefit from solids filtration, but it is not necessary. Worms in the media beds will help too.

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PostPosted: Jul 28th, '21, 03:28 
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As for the SLO, I have very good success without tilting the tank. It's all about setting up beneficial water flow. Here is a link to the details (scroll to the bottom of the page).

https://www.backyardaquaponics.com/forum/viewtopic.php?f=18&t=27808&p=576230#p576230

Note the T at the top of the SLO in the photos - the most important feature. The T acts as a siphon break but also an overflow if the inlet becomes sluggish or clogged.

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PostPosted: Jul 28th, '21, 11:24 
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oldmobie wrote:
a. Patch hole in middle tank where bulkhead was.


I'm sorry, what hole?


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PostPosted: Aug 12th, '21, 01:37 
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I found what I'll use for my first growbed. It was pretty affordable, seems tough enough, and was designed to serve as a planter or a fish pond. It's smaller than my previous growbed, and has a rolled edge on top with holes for mounting screws. I need to build a stand for it and then I'll install it. Gonna go sand & iAVS.

I've also stocked the middle tank with wild gathered duckweed and crawdads. I've been experimenting with my raft beds. I bought cheap cups that fit with an inch or so below water, the rest above. I drilled a bunch of holes in the bottom and I've been filling them with media and cuttings. I'm hoping this will let roots form in water and others above water, giving access to oxygen. Hoping it works kinda like kratky. Some plants like it better than others. Tomatoes are doing well, along with sweet potatoes, and comfrey. With other plants it's a mixed bag, some live some die. This seems to work better with perlite than sand. I just filled other cups with vermiculite today. Also added seed for the first time, lettuce.


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PostPosted: Aug 12th, '21, 04:11 
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I have the same tub. Bought at home depot. Original intended use is for mixing small amounts of concrete, but works just fine for some plants. Also available is a 10' long bed that can be used for growbed. You're going to spend a few more dollars, tho. But they will last for quite a while. Bought mine, with stand, before everything went crazy. You might contact them and see if you can buy direct. You will need to build your own support system if you buy the replacement one.
https://tarterusa.com/tarter-products/1 ... eeder#MSRP


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PostPosted: Aug 12th, '21, 04:29 
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I think the concrete mixing tubs I've seen are slightly smaller. (But otherwise seem identical.) I think this is 2' x 3'.


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PostPosted: Aug 17th, '21, 08:31 
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I got my little tub mounted on my very ugly table. I put a bulkhead in the bottom with an overflow pipe with some holes drilled at the bottom. I put the hose from my pump in it and watched it for a couple cycles. It doesn't run over, and it all drains to a depth equal to the thickness of the bulkhead. I got tired of working on stuff, but if it still looks good tomorrow, I hope to zip tie some fabric over the drain holes and put in the sand.

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