Backyard Aquaponics
A place to discuss aquaponics

Okay. I think I've gone as far as I can alone without crying for help. I have been trying to make a small test system work for months. a continuous flow system comprising two 50 liter containers nine goldfish in one, which I reckon is about the ceiling before they start to die, and pea gravel in the other. retic pipe in a circle, punctured to trickle feed the water to the crop, sits on the surface of the gravel. The containers are a foot deep.

Basically, plants will not grow well. We've been through 39 degrees here in perth and the plants are not thirsty, but they won't grow. tried bok choy, lettuce and now tomatoes. All the same story. branches of the current crop of tomatoes curl downward and leaves are underdeveloped. Water is clear and fish are fed 2ce a day. when system is switched off water goes alge and murky so I know nutrients are there but plants won't grow. system is six weeks old in current incarnation. TOmatoes in dirt nearby are four times the size.

I think it's the PH. It's way basic, above 8, and when I add more PH balanced water to compensate for evaporation it goes back to up of 8 within not long. Have tried adding vinegar to acidify things but within a day the PH goes back to "normal". I just dont get it, I thought I'd have problems on the other end of the PH scale.

Is it the pea gravel? the fish food? my haircut?

Can anyone help!

Cheers,

Durkis

It might just be the heat.....I ran a great graden last year on a pH of 8.1

If you could PLEASE post some pic's that would be grea , in helping diagnose the problem.....

If its continious flow, the root system could be developing root rot.....the root system needs to breath from time to time

probably the pea gravel, can you post some pics?

Ta! will post some real soon

From the initial description there are two things that jump out at me.

First, it sounds as if your grow bed is just getting the trickle of water but not flooding and draining. Please clarify this for us. Couple reasons for mentioning this, first if the bed is constantly flooded then there is probably not enough aeration for the plants to do well and the bio-filter bacteria will suffer lack of aeration as well. If the bed just has water trickling though it, then there are probably huge areas of dry gravel since it is nearly impossible to wet the gravel evenly without flood and drain. (you don't really want to wet the surface of the gravel, only all the gravel an inch below the surface.) With a trickle through bed, there is lots of dry gravel and therefor only small areas of wetted gravel to act as the bio-filter and therefor the system has trouble converting enough of the nutrients.

Second, the gravel. If you pea gravel is limestone gravel, that could easily be your problem. The high pH is ok for getting a system started but the plants would rather have a pH down in the 7 range. However, if your gravel is limestone, it doesn't matter how much acid you add, it will keep going back up to it's buffer level. This is not to say that a system can't operate at a pH of 8, it is sometimes more challenging though, certain plants may refuse to grow well due to nutrient lockout and the system might require extra supplementing. It sounds like you may be suffering some nutrient deficiencies so a cap full of seasol or maxicrop (be sure it is the kind with minimal nitrogen or phosphorus as you want the potassium and trace minerals mostly) might perk the plants up and some chleated iron may also help things out a bit.

A few other things to keep in mind. Seedlings often go through a stage just after getting a true leaf or two where they seem to do nothing for three weeks. During that time they are often simply working on growing roots. It can also take some time for a system to mature. A new system often takes 6 weeks or more to cycle. What are your water tests showing? Did you go through the normal cycling with an Ammonia spike and then a Nitrite spike and then rising Nitrates?

Aside from the lock out of nutrients at high ph, there are possibly two other factors. Fresh pea gravel has an ability to reduce phosphorus by adsorbtion, according to a study I read. The other is the fact that pea gravel gets very hot in Perth sunshine, perhaps a little shade?

TCL + A few other things to keep in mind. Seedlings often go through a stage just after getting a true leaf or two where they seem to do nothing for three weeks. During that time they are often simply working on growing roots.

Loosely=
root growth is during a waning moon, leaf growth is during a waxing moon

OK folks, here are the pictures. I have 2 pumps going in with the fishies, one pumping to the grow bed and one bubbling to keep it nice and oxygenated in the heat. The grow bed hose is connected to a 4 way junction, the two lateral junctions at either end of a circle of retic pipe, and the fourth continuing through the midle of the circle. Holes punched through the pipe with a drill. this does seem to keep the grow bed moist under the surface. The water does tend to get hot, but the pea gravel seems OK and these symptoms were soffered by bok choy and lettuce in much cooler weather. Bear in mind these plants are pushing 2 months of age so we can discount a nitrogen spike or root growth. PH tends to over 8.

For the tomatoes link http://www.hbci.com/~wenonah/min-def/tomatoes.htm
Still think it may be phosphorus and weather.
In my scruffy system had one silverbeet die completely and one suffer just after those easterly winds we had a few weeks back. Also lost a varigated yew in the garden.

That plant looks pretty far gone. And it does look like some sort of deficiency is the problem.

In the evening after the temp cools off a bit, try giving the plants a foliar feed (spray the leaves) with some seasol or maxicrop diluted according to the instructions on the bottle. If the plant perks up within a few days, then you have a solution (though perhaps not a good enough solution.) You can also foliar feed with liquid iron (make sure to do it in the evening after things cool off though since spraying these things right before or during the heat of the day can really scorch the plants.)

So what kind of rock is your pea gravel from? (Pea gravel describes the size/shape of the gravel and doesn't tell us what kind of rock it actually is.) If it is limestone, you probably need to get different gravel for your grow bed or you may be constantly struggling.

We have just been through a tough summer in Western Australia.....I was visiting a mates vegi patch in the progress , last weekend , and his tomato' s had the same rust......his thinking was the heat....stunting and runting the plants....

I was reading in the Diggers Handbook, photosynthesis stops at 35 oC, so burning, rust and stunting where to be the norm.. Might of just been to hot

Thats my take on it

Mainly lateritic ironstone gravel.
Its the oxides of iron and aluminium that bind the phosphorus (I think). Seasol may help with the K and and trace elements but it won't help with a P deficiency.
Normally there will be enough in a system through feed etc.
One of the reasons I suspect this is
"Water is clear and fish are fed 2ce a day. when system is switched off water goes alge and murky so I know nutrients are there but plants won't grow".

yeah it's lateritic gravel which is what all pea gravel is around here. Maybe I should just bite the bullet and switch to expanded clay as a growth medium. Will try the seasol first though. May also try some sort of mulch or shade.

Looks like too much heat form my view, what temps are you at in the fish tank? I don't think the ph matters much as 8 isnt that dang high might not be perfect but your not that far off. Temps would be the bet for me, your bed seems pretty small to be in that much sun. maybe shield the bucket a bit to help from cooking the roots?