Backyard Aquaponics
A place to discuss aquaponics

Yes Noddy, they're still eating well, although they dont seem very interested in late afternoon feeding in the past couple of days, I'm not sure why that is. They get stuck right in for breakfast though

I hope I am quite a long way from harvest, the trout only went in on 9th June, and I still have about 40kg of pellets! Yes, the 5mm are floating pellets.

Fortunately the weather is cooler again, max 22.8C today, so I didn't need to worry about water cooling, other than shading the sides of the GBs, and I'm continuing to run longer pump on times at night. As can be seen in the graph from Sunday, I think what I was doing was helping a little.

Making ice costs me nothing, off-grid solar makes sure of that! I'm freezing a big batch of 2l ice cream containers full of water each day this week. When it is sunny all day and I'm not using any large electrical loads, I have plenty of energy to spare, which is why I'd like to use a larger refrigeration unit to cool the system. The freezer is a huge 480 litre unit that was given to us, so plenty of space to store a huge quantity of coolness I run it at max cooling all day, and turn ot back a bit at night, to reduce battery depth of discharge a bit.

I picked, then pulled out all 4 of my pea plants today, along with a cabbage that went to seed, and the chooks had a great time with all the greenery. The purple peas were a bit disappointing taste wise, as they were when grown in the ground previously, plus they were covered in powdery mildew, which was showering over my chard! Frequent treatment with Eco Fungicide made no discernable difference, it was indesructable. I've heard peope say the mildew likes damp conditions, but it hasn't rained more than a 2 or 3 millimetres max a couple of times in the past couple of months, and mostly it has been very dry- 22% relative humidity a short time ago, and down to 14% yesterday afternoon.

I also picked another small cauliflower, so now I have a bit more space available, to plant more beetroot and some corn.


Rupe, yes they started on the 5mm with no hesitation this week, and I'm sure at least some of them would go for the 7mm too.


Away from the greenhouse, the cherries are all coming out in bloom now, so I'll have to get the fruit fly traps set up ASAP, the fly will probably be out early due to the continuing warm weather.

Very probably related to the water temp.... if you can feed morning and noon.. whack the feed into them...

And see how they go in the evening.....

Twice a day is fine.. if that's what your time table dictates...

Ah... at last.. a nice chilly breeze blowing off the Snowies... even a light drizzle...

The trout life... to die another day...

I had one death today not sure if it was my mistake with the hose the other day or water temps. Just about to do a water test now.

Powdery Mildew actually likes lack of rain. I live in a humid climate and our spring season tends to be our dry season and the powdery mildew can get really rampant. Supposedly the change in pH and the increase in potassium from the potassium bicarbonate sprays should help against it but if the plants are not producing an enjoyable crop anyway, then get rid of them. And if the mildew is really bad, then spraying may really be too late to help much. Be proactive when trying to combat the mildew and try to spray the crops before you really see signs of the mildew.

Milk diluted 1/10 is supposed to be the best powdery mildew spray but I've found I usually find it when crops are at their end anyway e.g. Cucumber, zucchini

We have previously tried diluted milk on the cucumbers in the dirt garden, but it never seemed to help at all.

Has to be full cream milk to be effective at all... and as TCL says, even with Potassium bicarbonate, which is more effective... you really need to be proactive...

Agreed, when I was involved in viticulture we sprayed for mildrew before we ever saw it, it was more like maintenance spray than reactive. Once mildew sets in its hard to kill.

Could it be caused by evaporation of the GBs passing by and condensing on the plants?

It has cooled down a bit during the past few days, although every day was still above average. In the coming week, Mon-Wed should be around average, with a decent amount of rain, which will cool my system water a bit more. Meanwhile, I'm stockpiling more ice, there is 80kg of it in the freezer now, with another 10kg of water cooling down today. I'll need to continue making ice to keep the AP system water below ~20C through any short hot spells of weather, in addition to the small refrigeration unit and underground cooling pipes. If there is an extended heatwave, I'm stuffed! ... at least the freezer will be, with small trout.

It sounds like a lot of ice, but for 6000litres of water, it takes about 50kg of ice just to cool it by one degree, with ice at -25C added to ~20C water. Energy wise, that's equivalent to running a 250W fridge with an effective coefficient of performance of 2, for about 14 hours/day. From my tests last week, my refrigeration should just about be able to do that, but it does require a bit more work with insulation, heat exchange efficiency, and I'll need to keep the radiator cooler than the air, probably with an intermittent fine spray of water.

Clearly, insulating the GBs is a lot more effective means of keeping the water temperature down, so I will be doing that as a first line of defence against the heat.





Heck, while I'm at it... as an example of how much heat energy the system is gaining during the day from the sun, say 9th Sept, the water temp increased 3 degrees, which requires 75.25MJ of energy for 6000litres of water. That's about 21kWh, equivalent to running a typical 2.4kW washing machine water heater for almost 9 hours! It would take about 150kg of ice to negate that heat gain. You can appreciate why prevention is better than cure- so insulation and shading is the first thing to do when trying to keep an AP system cool. Fortunately the system loses a lot of the heat into the atmosphere at night, although insulation will lessen that somewhat.

pH continues to fall, I put a 4l container of shell grit into the ST on 9/9, and also added 30g of Ca(OH)2. On 10/9 I added 10g of Ca(OH)2 and 10g of KOH on 11/9.

The Infinity 950 air pump is only pumping on one outlet due to a split diaphragm, so is only outputting maybe 200l/hr into the FT for the past 5 days, and I suspect the other side may be on the way out now, as there are less bubbles than there used to be. I've ordered a couple of much higher power and capacity air pumps, which should arrive next week, although so far I have not been able to get any of the 200mm round air stones I want to use. The trout aren't suffering though, and continue to mostly do laps of the tank with the circulation about half way down, as most of the oxygen is dissolved due to water returning to FT and ST, and a jet of water into the FT, plus the F&D cycle.

I sold another 6 bunches of chard yesterday and the chooks have been getting plenty of it too, as well as cabbage and cauli leaves. I've planted some corn and more beetroot, with a few other plants lincluding lettuce and squash to go in shortly when I free up some more space. The picked peas were quite nice in a stir fry, and some of the corn went in their place, and I'm about to start pulling chard out, as some of it has stated sending up the beginnings of seed heads, and it never tastes as good once that happens. I'll steam and freeze a fair bit of it for later, as we'll still have plenty fresh from younger plants.

I have ~40kg of fish pellets remaining, the fish are eating up to 200g on a good day, and the temperature is warming up....I can see that a large amount of food is going to be left over, unless they start eating dramaticaly more very soon, or else I force feed them!

Even if they were eating twice as much as they are now, that food would last to New year, and at the current rate it would last until next autumn, if I could keep the water cool enough.

I tipped 30g of 50% KOH into the ST this morning, over about 90 mins, as the pH is going down quite quickly now, down to pH6.56 yesterday afternoon. I'm not sure that adding more shell grit will help, the last 4litres hasn't stopped the drop, so I'll have to start with regular small doses of Ca(OH)2 and KOH.

I don't think that's why the fish aren't interested in their food though, they barely looked at breakfast this morning. Perhaps it was the 26mm of rain in showers and storms yesterday and overnight, or the low barometric pressure- around 1003 to 1005hPa SLC since last night.

Does anyone have any suggestions for a supplier of Murray Cod in (preferably northern) NSW?

Last of the first crop of cauliflowers, picked last night, it was a monster!

Weather can certainly put fish off their tucker.

Rain can also assist in lowering pH.

Shell grit and lime might help slow the pH drop but if your pH is falling that much even with lots of shell grit, you are right that you probably do need to keep up with regular doses of the Potassium Hydroxide and Calcium Hydroxide.

Now do keep in mind that there are plenty of people out there who run very successful systems at a lower pH, you just need to make sure the pH doesn't drop out the bottom or drop so fast that the bacteria can't adjust to it. If you do decide to let your pH run at a lower level, make sure you get a pH testing means that can measure low enough so you can be certain what your pH is and keep an eye on the ammonia level since if it starts to rise it could be a sign that the pH has dropped too much and you DO need to take action.

My good quality pH meter is very handy for keeping an eye on how things are going, and by monitoring the pH of water returning from the GBs, in the fish tank, and in the sump tank, I can tell when any alkali additions are fully mixed in. I can watch the relative change in pH through the flood and drain cycle too. The meter takes out the guesswork and estimations that come with coarse resolution test kits.
I prefer to keep the pH not too far from neutral, where I wont have any nutrient lockout problems, aren't to close to a level where the bacteria colony can collapse, and the fish don't have to work too hard to maintain their slightly alkaline balance internally. I'm quite happy to add KOH and Ca(OH)2 regularly, as I have large supplies of both. As I have been increasing the amount of feed, it's becoming clear that shell grit alone isn't enough to do the job.
I added 20g of Ca(OH)2 yesterday afternoon in addition to the KOH in the morning, it all goes into the ST, so it gets to move through the acidifying environment of the GBs before hitting the FT.
Today the aeration will be increasing when I hook up a new air pump to replace the rather tired Infinity unit that's pumping at about half capacity after only a few months work. T he system doesn't really require it at this stage, as there appears to be enough dissolved Oxygen in the water due to the cycling and water returns, however I think this it's a case of: if some is good, then more is better