My plants are doing lousy. pH?

[Louise]

Above is how my plants are doing in the ap-system after being in there for a few weeks.

And below is how their soil-planted fellows are doing, even though they were the same sizes before, and the soil-planted ones sat in their pots about a week longer:

The soil ones are almost three times bigger. The ap-plants are either not growing at all, such as the tomatoes and peppers, or growing but not looking healthy, such as the cucumber, basil and dill.

It's a newly constructed system, first time running. The fish are eating, though not a whole lot. I have about 50 tilapia about 10 grams each. The light is good, in a greenhouse. The temperatures are good, with water temperatures ranging from 18 degrees Celcius when I started to 22-26 degrees C now. The cycling went well, and today the values were: Ammonia 0, Nitrite 0,025, Nitrate 0,5.

The pH, however, has not been good, ever. It sits there at 8-9. It's not likely that it is my media (crushed lava in the bottom and Leca on top) that is raising the pH. My well water is at 7,5. My friend thinks it's algae that is raising pH. The water is dark green. Still haven't arranged to block more of the light.

What do you think is the problem? What would you do to solve it?

[Daniel]

The PH could very well be causing nutrient lockout, so you may need to add PH down (or another supplement to lower PH) a little at a time until you notice improvement in the PH level. However, you may also want to supplement with some Maxicrop or other seaweed supplement, since a new system probably will have difficultly supporting much plant growth until the fish are larger. Perhaps you could transplant the cucumbers and tomatoes to the dirt garden for now, and plant some lettuce or other leaf crop until your system gets a little older.

Just don't give up on Aquaponics yet - some things just take time!

[Louise]

I have no idea where I might get hold of seaweed extract here in Sweden. What type of shops keep it? I mean, there are not exactly a lot of shops for aquaponics or hydroponics around. Do they market it for other purposes?

[Vlad Jovanovic]

Hi Louise...You really have a lot of plants and heavy(er) feeders for a brand new system. Also, before you hop on the pH roller coaster with pH down products (acid) you really, really need to find the source of your pH woes. Whether it's the algae, or your media, or whatever...you need to figure out what it is that is raising your pH. Any kind of messing around with acid/pH down would be an exercise in futility until you isolate the cause first.

Media - Take a jar full of media rinse it, let it dry and then pour in some sort of acid (vinegar, HCL etc)... If the media fizzes lots of bubbles, it means there is an acid/base reaction going on (most often some type of carbonate in the rock).

Source water pH - Unless you set your well/tap water out in a glass for a few days to off-gas the trapped CO2 before you initially tested it's pH, you are probably getting a false low reading.

Algae - Yup, definitely can be responsible for diurnal pH swings. You can easilly test this by taking two pH readings one right before dawn, and one in the late afternoon. Compare the two. AND GET A MOVE ON AND BLOCK OUT AS MUCH EXCESS LIGHT EITHER WAY :)

Between these three things you may find one or more contributors to your pH problems. But really, be aware that your nutrient level, regardless of your pH at this point, is probably not enough to support (well) the type of plants you have in the numbers that you have them.

SM6 and SM3 seaweed extracts should be available to you in Sweden.

They are the same type of products as MaxiCrop/Kelpak/Seasol etc...only the extraction process' are different for each...which is not a concern, as the end result is a low NPK value product (which is what you're after) full of trace elements and plant hormones (auxins and cytokinins...those hormones are what those companies are all extracting in the first place).

Good luck.

[George]

Photo of your tank?

[Louise]

Here's a photo of my setup, the day I planted it (May 31st). Since then I added a raft bed on top of the IBC fish tank. So far just some tiny seedlings in the raft.

I didn't realise that I had to have fewer plants in the beginning. Sylvia's book said go ahead and plant already during cycling. But fine, then I'll move most of them to dirt somewhere. Probably leave the cucumbers and the Physalis, as they're looking reasonably ok. SM6 - seems a bit of a treasure hunt has to be undertaken. No hit with an internet search.

Should I try feeding my fish more often? They don't eat as eagerly as when I had them densely in an indoor aquarium. They were hatched there during this winter, and had really outgrown their aquarium by the time I moved them to the IBC. But it was a more than tenfold increase in space!

As for the pH:

I've tested the media, it's not that.

I'll try testing water that's been sitting, I haven't done that.

Light blocking - I can do some, but I think the raft bed is going to be the difficult one.

[Vlad Jovanovic]

You can plant lots of plants right away...if you like lettuce .

I swear my 8 cucumber plants suck nutrients comparable to like 200 lettuce plants...Especially magnesium and potassium (your cuke looks a little Mg starved in the pic)...

Yeah, you can feed your fish more and more often and...even if they don't eat it all, it'll rot and be mineralized anyways. Rotting fish food turns into ammonia (even without the help of being eaten by a fish)...

You know, you don't have to use the store bought seaweed extracts (unless you want the hormones that they come with)...they have about the same mineral value as plain sea water. I used sea salt that a friend had collected for me from the rocks on a stretch of coastline...and grew near a thousand harvestable plants out (mostly lettuces) during cycling...

[Daniel]

Vlad,

I am facing the same issue with cucumbers hogging nutrients in my outdoor system which was set up last September. I have great growth and lots of blooms, and even lots of inch long cucumbers. Then they seem to just quit growing and eventually dry up - but my leafy crops (sesame plants - for Korean dishes) are going wild! I keep adding some Maxicrop and a little Chelated Iron, but perhaps not enough to make the cucumbers happy. I'm assuming I just need to be patient and wait for my fish to be larger to support the amount of growth in my beds. Right now the bluegill I have are still all smaller than my palm.

I do have a question though about your comment on the extra food - conventional wisdom says not to overfeed the fish, but you seem to be indicated that overfeeding is not a big deal. Reasons?

[Vlad Jovanovic]

Well the cucumber thing could be a couple of things depending...If you planted a gynoecious, (all female flowers) parthenocarpic (self pollinating) variety, then your plant is definitely aborting fruit because it can't move (or doesn't have access to) the necessary plant essential elements to sustain the growing fruit.

If your cucumber variety is the 'old style' monoecious (plant has both male flowers as well as female flowers) then what you are seeing is due to a lack of pollination.

And of course the possibility exists (if you have a monoecious plant) that both of the above things (lack of pollination, and lack of plant essential elements) are at play.

Now I'm not advocating a general practice of over feeding, but if your bio-filter can handle it and your lacking in NO3- and/or other essential elements...why not? 

The fish don't really do anything all that special to the feed that worms and bacterial decay would't do. Decaying fish food would be a more potent plant input than fish feed that has had a good portion of it's mineral content stripped and used by the fish to be converted into muscle mass. Make sense?

Now, you probably don't want to (nor would you need to if you've sized and ratio-ed your system properly) make it a permanent practice to grossly overfeed...as you'd probably run the risk of overloading your bio-filter...That and it's probably a horribly inefficient practice from an economic standpoint. If (long term) your not using the feed in part to create fish bio-mass, before becoming plant food...there are way cheaper (or all out 'free') ways to do that.

I'm having pretty good luck extracting nutrients from stinging nettle and comfrey (which grow like crazy around here). Phosphorous (P) seems to be the limiting factor there, but luckily there is more P in fish effluent than there is nitrogen (N), so that's still not a problem even with a very light fish load....and in the smaller fish-less system I've been able to overcome the lack of P thing by using struvite that has been crystallized from humonia. (The struvite is a very powerful P fertilizer that costs me about 10 cents a pound to make...and is a fun exercise in biological phosphate reclamation)...So there is usually more than one way to 'skin a cat'...

Sometimes 'conventional wisdom' can be good, but it can really also put a big damper on growth/innovative problem solving blabla...

You can also foliar feed your cukes fresh brewd worm tea...or target specific plant essential elements in a foliar feed...I chose to use this 'dual root zone' thingy for my cukes in the new biggish AP system...and I'm glad that i did  http://community.theaquaponicsource.com/group/fish-less-systems/for...

[George]

Stinging Nettle and Comfrey - how do you extract the nutrients?

Overfeeding - If your oxygen and filtering is sufficient, that would be an interesting thing to try.  Increased nitrification should/may lower PH.

[Daniel]

Wow - Vlad, thanks for linking to the thread on dual root zone. You have some amazing growth in that setup!

I must have the gynoecious parthenocarpic variety of cukes because I am getting 1-2" cukes before they dry up - so pollination is not the problem. It sounds like you've confirmed by belief the little cukes are withering from lack of nutrients. I'll look into the foliar feeding to see if this might help. On the other thread you also mentioned pruning off fruit too far from the base - I think I may try this as well to see if I can get at least a few cukes to edible size rather than losing all of them.

I'll certainly consider the dual root thing for future plantings as well, though it is a little late for these plants...

[Tim Day]

Hi Louise!

Like Vlad said, sorting out that pH is definitely your first priority. Did you use any DIY components that might not have been cleaned properly? Where did your raft come from?

If you have some sort of buffer in there (carbonate hardness of your water even) pH can stay still and then jump all of a sudden, so it's good to be slow when adding acid to avoid the pH rollercoaster. Nutrients such as iron have no chance of being efficiently consumed at pH levels as high as you have, and your plants will be susceptible to disease and pests.

In your photos your plants, to me, look like they are suffering from a nitrogen deficiency. Your nitrate levels are pretty low and you do have some heavy feeders in there so I would definitely agree that adding some seaweed emulsion would be a good idea. And feed your fish as much as they will eat! As they get bigger and eat more nitrogen shouldn't ever be a problem.

For picking nutrient deficiencies everyone should check out the flow charts in this link - they are awesome and I love them. http://landresources.montana.edu/NM/Modules/Module9.pdf

So here's what I would do:

1. Find out why pH is high. Fix the root of the problem.

2. Adjust it down slowly slowly. I use only one cap at a time, wait a couple of hours, test, then add another if needed.

3. Get the nitrate levels up either by feeding your fish more, adding some seaweed emulsion (but not so much that your ammonia levels go too high), or both.

Once you are established you will be pumping out the greens! Good luck!