Backyard Aquaponics
A place to discuss aquaponics

We started December well above average temps, in town was 8C above average for the first 5 days of December with a couple of 38s and also 2 40C days. Fortunately it was a bit cooler here, but still uncomfortably hot for me, and maybe the trout, who haven't been very hungry.

With the reduced daytime pumping times, increased at night, and coverings over a fair bit of exposed GB surface, and misting sprays of water a few times per day. I've managed to keep the temps ok for the trout, with no losses.
With good aeration and not many fish left in there, they have been swimming around in the lower half of the tank with no signs of Oxygen deficiency.



They haven't been hungry, and have had under 150g of pellets in the past week, and none for the past few days. There are still a few large trout in there, and any small ones I'll put in the large system, leaving the Murray Cod, which I caught and released again the other night.
Catching them might be a 2 person job now, they can see the net coming due to moonlight in the evenings, so we might have to herd them into the net.

I think there are are good levels of nutrients in the system ( fish poo deliberately left in the ST in recent weeks, plus what is in the GB media), but I'll drain some water from the big system into this one every now and then to keep the tomatoes, capsicums etc powering along until the weather cools down in autumn.

Hi Gordon... you might remember that I was foolish enough to give Murray cod a try... haven't lost any for a while but they're a far cry from jade perch when it comes to growth rates so far.

Very interested in how big your sole survivor is... and a reminder about how long you've had it.

Hey Dave, the MC has been in there almost 3 years now, and I reckon it is no more than 350g and 250? mm long... but I was handling it in the dark, so its just a guesstimate. The dorsal fin is a bit spiky, which is how I could tell I had the MC, rather than a trout, as I couldn't see it very well under just starlight.

Thanks Gordon. I suppose it's had to complete with 3 generations of hungry trout. But I'm starting to think it'll be a long time before I taste any Murray cod.

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Yes, at best they only grew at half the rate of Rainbow Trout for me, and mostly even slower than that.

Hi Gordon what is the longest pump off time you dare to do in the day time? and do you have one of your charts showing whether it makes a helpful difference?
I was thinking about this because when the GB's drain out and are not refilled for a long time they'd draw in the hot air and continue to be heated all over and store that heat until the next cycle comes along converts and delivers warmer than normal water back to the FT.

Pete.

It is currently off for 2 hours at a time in between 5 minute pumps through a fair part of the day.

I'll have to dig through my data to find an example with a similar temperature range and min and max, but I can say now that it does make a difference.

Whilst a small amount of hot air is drawn in, it is cooled on the way in by wet media, which has a much greater heat capacity, so the air is cooled down to a bit above the dew point of the air. This is helped in my case by the media being covered with wet material, which I frequently dampen, so it is always cooler than the air, providing cooling to the media as the air passes through it and into the GB.
Any surface of water in the shade will always be significantly cooler than the air in typical summer temperatures, thanks to the latent heat of vaporisation of water, and the cooling effect is greater when the relative humidity is lower.

These 2 are reasonably close in air temperature profile, the early Nov plot when the pumps were running longer has a >1.5 times greater water temperature range, and you can see the pauses from where one of the 3 timers has a failed relay, meaning no pumping every 3rd hour. As I'd expect, the pauses are not so obvious with the very short pumping times.




Each plot is for 24 hours starting at midnight, x scale is in minutes

Thanks Gordon, what sort of material are you covering the GB surface with?

Pete.

All sorts of things, mainly to avoid spending any money. There's some leftover 50mm polyester insulation, which works really well, but does tend to lose a few fibres, which I don't really want to have floating around the system. The mush at the bottom of the media will no doubt retain most of it though.

There's a couple of old towels, socks, shirts, the exfoliated fibrous stuff from the bamboo clumpand a fair amount of bits of fibrous material from the banana leaves. Anything to shade the bed that doesn't break down quickly, and preferably hold a bit of moisture will work, and lighter colours are better.

Of course I only need to cover areas that dont have plant cover, and that will include most of my outside GB shortly, when I pull the dying pea plants and garlic, and replace with rhubarb.

I was wondering if the towels etc. could be moisened by a higher flood level so the evap-cooling would happen automatically what do you think?

Pete.

That's what happens with mine early each morning when I run a long flood cycle , but eventually they will turn green, although that isn't really a problem.

I removed the old pea plants along with the garlic from the outside GB yesterday, below is the garlic.
Rhubarb crowns to go in their place shortly.

Last night's trout dinner, the sauce is cherries and the little nuggets from the flower heads of chives and garlic, and we also had some home made chunky guacamole. The trout was 959g out of the tank on 29/11, and 835g after gutting etc.



The water temp has been ok recently, but the weather is forecast to be very hot over the coming week, so I'll be monitoring the temperature closely.

Yesterday I installed a Hailea V-60 air pump on to replace the SunSun 60lpm, it is much quieter, and uses 35W rather than the Sun Sun's 55W(claimed, actual ~48W), although the ~0.6 power factor means the inverter is still working to produce 55VA, although it is still significantly less than the SunSun's 78VA. At some stage I'll probably correct the pf to nearer unity with 2.5uF caps.
The pump is very quiet, and can only be noticed when near it, and with my muffler, it doesn't transmit any noise to the FT via the 25mm poly piping.

The strawberries are producing very well, although something which hides in daylight, is eating the occasional fruit... maybe a slug. I'll have to have a search and destroy mission by torchlight!

We bought a misting system from the big B store, each mister only uses 3litres per hour, so we are going to set up 8 misters in the GH on a timer for use on hot days to see if that makes much of a difference in hot weather.

Water and air temps for Dec 7 to 25th