The shell grit seed raising seems to have worked.

There was some slight discolouration on some leaves that I think might be due to nutrient lockout because the pH is probably off the chart in that local area, but generally speaking, I think it works. The discolouration is not shown well on this pic. The true colour is closer to the lettuce leaf on the left.



When pH is at certain levels, various elements become less available. If your system sits at about pH 7.0 then everything is available.

I just lifted my first seedling out of the shell grit, and it had a 24cm root that came out in tact. I made no attempt to be gentle and just lifted it out. I tried another one and achieved the same result.

Anyway, no washing - not even a rinse, and three tiny bits of shell grit was all there was stuck to the roots.

I think I should have left it a little longer because there were hardly any side roots developed, but I planted it next to some existing established kale, so I'll have something to compare it with. The existing kale was planted around ten days earlier.

I add some seasol® from time to time, so I might add it directly into the shell grit once I see sprouts to make sure there are extra trace elements available next time. The slight discolouration might also be due to lower oxygen levels as the water probably moves quite slowly through the fine particles. I might sive the shell grit so I can get a slightly bigger particle size. I plan on reusing it for ever, so it's no big deal to sieve it.



120 Things in 20 years thinks raising seedlings in shell grit feels like a success

Aquaponics - Shell grit seed raising bee and gecko visitors

I found a little helper in my shell grit seed raising trial.

This gecko is tiny!












I also found a bee.

That's two now this year I think.

It left soon after I saw it visit my freshly transplanted wild rocket.

But my bee came back a little while later.

At least I think it was the same bee.

It certainly looked and behaved like the previous bee.

She looks busy.







120 Things in 20 years is now a bee keeper. I keep a bee.

Aquaponics - Shell grit seed raising shoots

My attempt at raising seedlings in shell grit seems to have worked.

No real surprise there, because if it's going to fail it wont be for a while yet. The point of failure, if there is one, will be the plants rotting because the water might flow through too slowly, and become stagnant.

The shoots appeared this morning.

The lettuce and rocket have sprouted, but the kale is yet to.

I think it was only 4 days ago that they were sown.

On a slightly interesting note, the seeds that were directly sown to the growbed came up yesterday afternoon.

They were sown around 10 days ago. I figured they weren't going to show and moved on to trying the shell grit idea.






I still think it will be better to grow seedlings and transplant them just so you can space the plants properly. When you direct sow, you have to plant lots of extra and think them out because some don't grow, and some move around a bit and as a result you can get clumps of seedlings all in one spot.

Anyway...

So far so good with the seed raising in shell grit experiment.

120 Things in 20 years still has no taglines forming in its addled brain.

Aquaponics - Shell grit seed raising

It seems like I've been trying for ages to find a decent method to raise seedlings from seeds.

My preferred method would be to just throw them all over the place and see what happens, but I suspect the clay ball media allows seeds to fall way down into it. It's possible that with the normal vibrations of city life, that the seeds fall all the way down into the water and then sink to the bottom and rot.

One problem with raising seeds in potting mix is that you do a lot of damage to the roots when you wash them before transplanting them into the aquaponics system.

I add shell grit to the system as a pH adjuster. The nitrifying bacteria tend to move the system toward the acid side, and the shell grit brings the pH back into line (approx pH 7.0).

So I figured it might be a good idea to raise my seedlings in shellgrit.

I started with a food container, and drilled a few holes around the base.

Then added the mesh from a stainless steel sieve, and filled it with shell grit.

Shell grit can be bought where ever you might buy chicken feed, as they sell it to people who have chickens. Chickens eat it and it helps make their eggshells strong.

I chose a space close to the water inlet in the growbed to bury it so the water flowing through would have high levels of dissolved oxygen. I figured this might be important as the flow through the tightly packed shell grit would be slow.

I buried it at a depth so the water level just reached the shell grit. The water "wicks" up through the shell grit so it stays moist.

I also added a lid in the form of another food container.











I'm not sure if the lid is needed, but a lot of store bought seed raising trays have lids so I thought I'd add one. It probably isn't required because I'd guess the lids are used to keep the moisture in, but with water always wicking up from the bottom...

Who knows.

I have no idea if this will work, but as always, I'll let you know one way or the other.


120 Things in 20 years - My ribs hurt.

Aquaponics - Fish waste solids masticator

I guess it's just plain laziness, but I'd rather not chew my fish's solid waste.

Luckily shell grit is willing to do it for me.

This is as yet untested, and in my experiments so far, there are some potential stumbling blocks to overcome, but this is what I'm working on...

We need shell grit in the system to buffer pH, so I figured I'd put it to use to break down solid fish waste, before it enters the grow bed. This is probably unnecessary, but I'm hoping to distribute the waste more evenly throughout the grow bed. I'm also hoping to grow some strawberries in PVC pipes at some stage, so it will be necessary to have very clear water running through them so they don't block, as the roots will almost fill the pipes.

This represents a possible solution to keeping the water moving freely throughout my system, if I end up needing it.

The general idea is that fish solids enter with the water, and because of the direction of the inlet flow, they swirl around. The water overflows leaving the solids behind. In aquaculture, and sometimes in very densely populated aquaponics systems, this is employed with a tap at the bottom to allow removal of the solids from time to time.. It's called a swirl filter or solids filter. All I'm thinking about doing is adding shell grit to one, and making the grit and the solids tumble around until the solids get small enough that they rise up and overflow in the grow bed with the water. I don't want to lose my solid waste because me plants want all the nutrition that's in it. The general idea is that it should be a prefilter, and double as a way to add calcium carbonate.

In my larger system, I think I will incorporate a solids remover in case something goes wrong and I need to instantly lessen the nutrient load. I wont need to empty it in normal use, but I will have the option in an emergency.

Aquaponics - pH buffering

In aquaponics, one issue that can effect your success rate is the pH of your water. pH is a measure of water's (or soil's or whatever's) level of acidity and alkalinity. A pH of 7.0 is considered neutral and also is what pure water measures.

Actually when we measure pH what we are really doing is comparing the relative quantities of two molecules. The hydrogen ion H+ gives us acidity, and the hydroxyl ion OH- gives us alkalinity.

The process of nitrification is acidifying, but in aquaponics we aim for roughly neutral water around the pH 7.0 mark. Depending on the media you use in your garden beds, your system's pH might not be close enough to 7.0 for your liking. Because the bacteria tend to make their world a little more acidic, the water will dissolve anything more alkaline than the current pH of the water. What this means is, if you have something like calcium carbonate, say in the form of shell grit* in your system, your clever system becomes self adjusting. Shell grit seems to have a pH of around 7.6. The more acidic your water gets, the more shell grit gets dissolved. This brings the system back into equilibrium. The shell grit will last for many years (depending on how much acid there is).

The shell grit is trying to get the water to pH 7.6, and the bacteria are forcing the water toward 6.0. Hopefully the result is your ph settles somewhere near 7.0 and everything gets along just fine. Plants also seem to enjoy a pH of 7.0, and that pH level also allows for the maximum availability of various trace elements to be liberated from the system and offered around to anything that wants them.

Shifting an aquaponics system toward acidity is a little harder. Most people add lemon juice, or vinegar. The test pictured to the left is the one at the top of the page but with 2 drops of lemon juice added. The problem with adding acid is that it would have to be done on a regular basis which is why we need to be careful not to use anything too alkaline as our grow bed media. Some people have gotten into trouble with limestone and marble.

Over the last few days I've been doing experiments with softwood charcoal, and have found it to steer a system toward being more acidic on an ongoing basis. The tests have only been going for a few weeks. The problem of a too alkaline system needs to be avoided from the outset, but if you have very alkaline water (say from a bore) charcoal might be a good way to pre-treat your top-up water and the initial water you use in your aquaponics system.



*shell grit is available for a few dollars a bag wherever you can buy chicken feed. Its made by crushing oyster shells or similar. Chickens eat it for the calcium they need to make egg shells.You can also use egg shells or snail shells for pH control in your system.