Backyard Aquaponics
A place to discuss aquaponics

Any ideas as to what can cause stunted growth in tomato plants? I bought 6 plants, put 3 in the grow bed and 3 in pots. The ones in the grow bed are less than half the size of the ones in the pots (which is a bit embarrassing since I have been spouting off to my wife and everyone else about how great aquaponics is).
My system is;
-Half wine barrel with about 5 gold fish. (had 6 but one just died.)
-Small plastic tub grow bed with 10mm gravel about 400 mm deep.
-timer operates about 4 times a day flooding the system for approx 15 minutes then draining away.

I checked the ph about a week ago and it was off the charts so I mixed a cup vinegar in 2lt of water and tipped it in. That brought the pH back to 7.

Any thoughts?

AP is highy variable with systems. In small systems plants in soils/wicking beds will generally always outperform the AP. It is only when you are optimum-high stocked with dirty fish (fish eating and crapping lots) and the systems are mature with lots of mineralised wastes that you really see the incredible growth (ie. at least 12 months) .

here are some things that may affect newer systems:

(a) whether the system has actually cycled..... (ie. no nitrates = no plant food)

(b) the water temperature - if cooler it can affect tomatoes as they like it warm
(usually a spring thing because soil gets warmer)

(c) nutrients - AP only produces a few things, mostly nitrates.
so the rest can only come from what you feed fish or else you have to add to get to plants needs.

(d) the system - its location, depth of grow beds, type of media, location relative to sunlight etc etc
the size of the system and pH etc.

you describe a pretty small system, so maybe a picture would help.


As an honest answer the main benefit of an AP is that over hot summers it allows plants to survive that boom and bust of the normal watering cycle. For some plants the slower growth in AP actually means they may yield more in the longer run and be less inclined to bolt, go woody/fibrous or go to seed.

If you just want fast dense growth then go to wicking beds.
Then you have all the advantages of organics and being able to add what you like.
and you still ensure a good water supply.

yes there are photos of massive growth but that is only from some systems...
it is a bit of an AP myth that you chuck in some fish and plants go beserk.

you should be doing these things in a controlled manner not just throw something like vinegar in to balance the pH.... vinegar can actually kill the bacteria. You need to be aware of the chemistry implications of what you add.
Hence around here muriatic acid (HCL) and similar is recommended since the by products are favourable to the system.

how long has the system been going and has it cycled ?

what does "off the charts" mean ?


in a small system issues are magnified / exaggerated because you don't have the volume of water to spread out the variants.

>> timer operates about 4 times a day flooding the system for approx 15 minutes then draining away.

that is probably not enough to keep the plants accessing the available nutrients.


p.s. to post above. AP grows really good lettuce (of correct types - particularly Cos etc) simply because it provides mainly nitrates from ammonia 'wastes'. Beyond that it really depends.

One thing that stands out to me is that with the high pH plants won't take up nutrients as well if at all.Try to run your system around 6.5-6.8.

any system with pH 6.5 to 7.8 will grow fish and veg just fine.

lots of members here for various reasons beyond their control run systems in the 7.8 to 8.2.
They quickly/eventually learnt that constantly playing with pH is poor advice and ultimately just adapt the plant feeding to grow bed based and foliar additives.

it is worse to constantly mess around with system pH than it is to run a stable system and adapt accordingly.

I suspect the issues here mostly relate to very trivial ones to do with a small-immature system rather than anything else. It is pretty much par for the course. Added to that vinegar isn't particularly high on the encourages plant growth list...

I have been tinkering around for the last 4 or 5 years with this system but I have never had much success with plants. It may be, like someone said, problems seem to be accentuated with smaller systems. I want to get the bugs ironed out with this one so I can finish the 1000lt one that I have been working on. I want to stock it with silver perch initially and if I keep the water at the right temp (22C) I would like to put in trout because they mature quicker. In the meantime I have been visiting Pontianak in West Borneo and helping them develop a system.

what does "off the charts" mean ?

The highest reading on the colour chart in my test kit is 10 and it was darker than that.

Finally managed to upload a photo.

the growth is pretty much what I would expect for a small setup like that.
you might get a bit more by increasing the water flow and the water plants would take a bi of the nutrients.
But I doubt you will get much of a serious tomato bush.

Wonder about your off-the chart values...
pH is exponential so pH 10 is extraordinary value to have - if correct that makes it very alkaline.
Doubt a set up like that could get there.

The wood barrel doesn't look lined ? Surprised it doesn't leak as I had one of these for a while and it needed a liner.

>> In the meantime I have been visiting Pontianak in West Borneo and helping them develop a system.

what does this involve ? (I like Kuching and Sarawak - nice area and not many tourists)

I'm learning this at the moment. I suppose it's more about the journey and not getting caught up thinking about destination ..... we all want big ass plants year round, if only it was so easy hahaha

on the ball there Kaz.. but the whole approach in contrast to dirt gardening is pretty good. I run a modest system (actually 5 smaller ones at present that add up to 3000 litres of fish tank) plus 3 wicking beds and various containers and over last few months season changeover I have pulled over 30-50 spring onions, 20-30 leeks, 8 beet roots, heaps of chillis, heaps of lettuce and spinach plus countless other bits and pieces).
So it is viable - it just takes time to get to the point of system maturity, system understanding/tweaking and experience that systems are generating. My tomatoes this season are a flop but I have gone with wrong varieties and not enough time to do the system mods I planned for spring. I do this using much less water than any dirt gardener would.

Well my tomato's are looking pretty good considering I've been going cold turkey for 2 weeks . no fish, no fertilizer and a unlevel grow bed hahaha ..... I must be doing something right? ......... if the few fish I added, seaweed liquid and blood and bone ... if that does the trick - I'm laughing ... fingers crossed lol