Backyard Aquaponics
A place to discuss aquaponics

Very clever... guessin you havnt got that test kit yet then. Arent you the least bit interested?

To move the solids around in your big tank a wavemaker power head pump might work they just shift water horizontal lots and lots for very little power eg 12000lh for 25w in my tank algae forms on the walls and drops down and creates a big pile hard up against the wall .
Rob

A wavemaker power head pump could well be just what I need to move big tank water, Terra, so thanks. In addition to increasing the removal of solids through my drains, I am keen to mix the water to reduce stratafication. At 25W power consumption the overhead should be affordable, as well.
I have been thinking about trying to make a vertical axis wind turbine (VAWT) for this task, with a view to mounting it adjacent to, or floating it in, the big tank. Since it will probably never get off the drawing board, a wavemaker power head pump could be the convenient and time-saving solution, even if less 'green'.

From what I have read VAWT's in general are not as good as a HAWT. Especially given it looks like you have the space to put it at a decent height.

That said depending on your wind levels solar might be more effective. A cheap weather meter with a pc link to monitor the actual wind for a few months is worth it if your considering going that route.
If nothing else it lets you know what speed winds to design/buy it for.

Someone mentioned passionfruit earlier. I have not had a issue with roots, have 2 in one bathtub. Every 2-3 months I do pull out a few roots from the siphon but not been major.
However the passionfruit is really sucking down the nutrients and has now covered a huge area. It's all I bothered to grow this winter as the few pea's etc I planted did not take off that well with only 5ppm Nitrates.

You are right about VAWT vs HAWT for power production from wind, Privatteer, but I was referring to just translating air movement into some water movement. I reckon a small VAWT would be much easier to knock up and more stable on something like a pontoon in the tank.
I have plans to install a 2kW+ HAWT to feed into my 5kW inverter, which is currently fed by just 3kW of solar panels. I got in just in time to secure the 47c per kW buy back deal offered in conjunction by state and federal governments last year.

Lucky. Just remember you can't change or upgrade the inverter.
I am assuming it must have 2 MPPT string inputs for you to be considering doing that.

To my frustration I just missed out installing the 2nd stage of my solar on a shed so now I am stuck with just a SMA 1700.

I didn't know that I couldn't upgrade the inverter but I knew it would be expensive to do so. That is why I paid a lot extra for the 5kW size, rather than just installing the 3kW one which would have done the job for my current solar power output.
Re your second stage solar array planned for your shed roof, is it not worth your while even without the REBS component?
Have you noticed how much cheaper these systems are now that the government rebate is gone?

Same thing seemed to happen with the LPG conversions for cars. Government offered a $2000 rebate and the cost of installing them seemed to up by that amount.

First home owners grant , same thing

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If you or I change the inverter or install an additional one we lose the 40c rebate on the original system. We are only allowed to add additional solar to the existing units capacity.

Eventually it might be worth it if they keep hiking up the power costs. But for now the rebate is mostly offsetting my import usage.
Without the rebate I would have to go for a lot larger system to achieve the same effect.

Anyone see a pattern here ?

Interesting pattern. I was thinking about that as I typed my last post.
Anyway back to my system, today I installed an eductor on the end of my filtered water return pipe. It fairly shoots the water back into the tank but I can only assume that there will be an increase in dissolved oxygen in the FT water as a result. At the very least I get more water movement.
How does one test for DO?

DO meters are expensive; but the fish will start gulping at the surface if they don't have enough oxygen.

Usually as long as you have splashing water and an air pump you should be fine.

Charlie, you shamed me. I finally procured a test kit today.
Here are my trout tank water test results, as requested:
pH: 7.0
Ammonia: ~0.2 ppm
Nitrite: 0 ppm
Nitrate: ~4 ppm

Haha, I am familiar with the piscatorial equivalent of the 'canary in the coal mine' test, thanks LowCarbTNPer! I was more interested in testing for the delta improvement after making a change to my set-up. It would be good to be able to quantify some of the variables of a system. For instance, by my fish behaviour I can tell that they have ample oxygen right now. That is no real indication, however, of whether the same amount of DO will be enough once the fish grow larger, or when the water warms several degrees, or both.