Backyard Aquaponics
A place to discuss aquaponics

I would say not.

I am having excellent growth in my growbeds, but all new growth in the nft is very pale, almost white. After discussions with our resident hydro guru, I have tested the system in the fish tank and in the sump. The readings were as follows:

Nitrates in fish tank- 10
Nitrates in sump- 0

I conclude that the plants in the NFT are suffering from general nutrient deficiency

At this stage, as the water passes thru the gb's all nutrients are being stripped. As the NFT is getting filtered water from the sump, the plants inthere are suffering.

An interesting experiment will be to see how the NFT goes after the addition of a decent number of fish. I will test the levels again in a couple of weeks. I expect that once the nutrients get to say 100 in the fish tank, they will be available thru the system.

I tend to think that the with the sheer size of your growbeds that you're correct Stu... and the tests corroborate that.....



I take it that you going to add fish to the main tank not to the sump.....

I've a feeling that upping the number of fish in the main tank will provide an excess of nutrients that'll pass through to the NFT trays..... unless of course the growbed plants suck them all up....

An alternative would be to install a bypass feed directly to a seperate drum bio-filter then feed the NFT trays.....

For lettuce and leafy greens, you're not going to need huge nitrate levels.... obviously this will depend on the sheer number of plants.... but you can always add more trays

I just realised this test was fundamentally flawed. I know why the nitrate levels read zero coming from the sump (and I am too embarrased to tell you )

Just think about this. If water is being pumped from the sump to the tank, and water in the sump is zero and the tank is 10 where are the nitrates being produced? I am not the brightest spark, but unless the fish are shitting nitrates instead of ammonia, I have cocked up the test and will re-do it differently tomorrow, and report back. What I really need to test, is water coming out of the fish tanks and water coming out of the growbeds to see how much of the nutes are actually being stripped in the growbeds, as that is the water that will end up in the sump and therefore feed to the nft.

Wasn't that what you did Stu.... test the water going into the sump from the growbeds...?

Confused.... I'lll have to revisit your system setup.

So you fill the sump from the growbeds, then pump to NFT... then back to sump and pump back to tank??? Correct???

Need to test water for nitrates going into the growbeds and exiting the growbeds.... no??

I'd read elsewhere on this forum that this wasn't the case - someone had the same concerns & tested it.

I tried searching for the relevant post, but the search on this forum is *frack* so ... :shrug:

I thought it was someone in the Carribean who had a system with lots of lettuce growing in pots sitting in PVC pipe ... I can visualise it in my head!

yep rupe. as above

..... twice in a day I've skimmed..... too much going on.... ahhhhh

geez mate you are heading into Les' league. Next you will be forgetting to put your false teeth in

Shoowt mi if i dooo .... :gummysmile:

All systems are different the water in my system runs here there and everywhere and on testing all the tests are virtually the same [ie the glass house runs on only a 10%percent changeover of fish water and the tomatoes are growing just as well as in the 100% of fish water]

yep, purpose of all this is to try and work out why the plants in the gb's are kickin ass and the nft suck

Still reckon it's the size and number of your growbeds in ratio to your fish Stu..... them's big beds

http://www.rutec.com/Manual/DEFICIENCY%20SYMPTOMS.pdf
symptoms of deficiency, iron and some trace metals are the only ones that cause white chlorosis in leaves...maybe the plants in gravel are picking up iron from direct contact with the rock. Maybe this iron is insoluble because it isn't chelated, so it doesn't make it through to the NFTs. Can't hurt to try some chelated iron.

have put some in, but due to the large water levels (ie 10000 litres approx all up, it is hard to know how much stuff to add

What's your flow rate through NFT?

Are all the nft plants doing poorly or just the ones at the ends of the channels?