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PostPosted: Nov 15th, '17, 14:26 
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danny wrote:
I wonder if earth piling against the northern face, and a coat of white emulsion would make any difference to the temps in PLJ's giant concrete tank?

I guess trees and bushes for shade would help in the long run too, but perhaps its all rather a lot of effort for a mere degree or two?...


Danny, I've thought about heaping sand against the western perimeter of the tank to mitigate against the scorching afternoon sun in summer but there are other factors to take into account. I've planted a semi-circle of tall-growing bamboo on this side which helps cool the area generally and provides shade specifically at some point in the late afternoon (I should check when that is). The large thermal mass allowed the trout to survive through to mid December in the early years but, as I've added growbeds, the water has warmed appreciably sooner each year (last year was exception due to late onset off summer) due to its greater exposure to the ambient temperature via the sun on the media, growbed surfaces, pipes, etc. Erecting shadecloth over the whole set-up would greatly assist, I'm sure, but isn't a cheap nor particularly simple exercise.

It was recently suggested to me by a free-thinking non-expert that I could cover the walls of the tank with pieces of polystyrene/styrofoam, such as from broccoli boxes, held in place with chicken mesh. I'm pretty sure that would be reasonably effective and l am toying with the idea. It is certainly a low cost method of mitigating rising (and falling) temperatures.

As for '... a mere degree or two...', that temperature differential could be the difference between having an extra week or two to safely harvest remaining fish and catastrophic loss of scores, or even hundreds, of fish ahead of expectations. Each little modification or innovation may only give incremental temp mitigation but, aggregated, they could equate to the difference between trout still feeding in mid December compared to all trout going fins-up in early November. That happened a few years ago and I hope never to experience it again. Viewing the trout death photos you posted caused me flashbacks.

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PostPosted: Nov 15th, '17, 18:57 
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I see what you mean about a mere degree or two being very significant with your tank size and numbers of fish. The polystyrene sounds like a good idea and the bamboo is clearly the most time effective solution in terms of shade via plants, and the canes are useful too!

I can see how the addition of GBs has led to the temp issues... I guess apart from shade and insulation the only other possible cooling action is by evaporation etc like joblows misting and hosing technique. Perhaps some kind of small adjustable drainage holes that would bleed a small amount of water into some absorbent cladding around the GBs with each cycle, so that the cladding can be maintained moist and evaporative action cools the GBs a little bit... Although I imagine you have given these kind of solutions plenty of thought already!

I can only imagine the trauma of losing such a number of fish :(


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PostPosted: Nov 15th, '17, 23:50 
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Hi PLJ and all,

I think heaping on dirt on the side of the tank is just delaying the inevitable - dirt is still getting heated by the sun (and accumulating and getting more the next day).

I think it would have to be a littl more elaborate: You need a space between the tank and the dirt (if dirt is what you want).....what it comes down to is 2 things:

- avoid direct sun
- air circulation

So - vaguely remembering your "public swimming pool" - I would paint the "sunny side" white - then, with some distance - "so you can walk in there"(1.0-1.5m) away, errect a some wall, tall enough to shade the pool sides (galvanized roof stuff, pallet wall, etc...) - if the stuff is paintable - paint it white too no the sunny side!!

Get the fence/wall all the way to the bottom, so no air can come in from the "hot side"
If you can afford it - some serious big hose/pipe/duct from a shady spot on the southern (NO sunny side) to duct air from there into the space between the tank and the shade wall.

If you want to go wild - try some netting for evaporative cooling in there too!


The thing with styrofoam (and other isolants) is, they work great to "dam" a constant flow (like a keeping a greenhouse warm agaist a cold outside environment) - in a case like yours, temperatures WILL equalize, after all it's all outside!
Isolants will only slow down the up/down cycles over the day/night, but after a few days it's going to be ALL along one average...

HOWEVER with the above stuff, you try to avoid radiation heat doing it's thing!! And that is a permanent arrangement!
IF you can do a evaporative something - you might even be able to cool down the pool-wall!!

Did you already cover the pool?? 55-gal drums-float as a center-pole and a tarp over the whole thing!! No more water heating!!

....and on and on and on!!

Cheers,

thjakits

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PostPosted: Nov 16th, '17, 10:27 
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In my systems only a relatively minor amount of water heating is due to the FT. Most of the water heating is via the GBs, so I think it is important to shade and insulate them before the FT if you have limited time/funds for the job.

It would take evaporating many hundreds of litres of water per day to keep a large system like this cool enough for trout (and then, only just). In my testing quite a few years ago I found that it is difficult to get the material from which the water is evaporating to much below 20C on hot days (it does depend on the dew point, works better if it is down near 0C). Certainly it can help limit temperature rise, but for required trout temperatures, you wont get much actual system water cooling.

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PostPosted: Nov 16th, '17, 17:29 
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I'm with Gunagulla, I covered up the grow beds and hosed them down, I didn't want to turn the pump off so the main aim was to cool the heatsinks as best I could.

After spending the last 2 previous nights up until 1:00am hosing and misting just to drop the temperatures down from 22.8c to 22.6c was a massive effort and I would have been harvesting fish today except we are now having some much cooler weather and will have a few more days of it yet.

It takes a lot to get 2,000 litres of water to cool down when it's been warming up for days, I don't know how you guys with larger volumes of water than my 2,000 litres can drop the temperature at all.

I wont be trying to drop the temperature down again next week when it starts getting hot again, I'll harvest before then.

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PostPosted: Nov 16th, '17, 18:17 
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Last summer I did all those things too as well as freezing plastic milk containers day and overnight.
Over the last few weeks I've been preparing the cooling devices and found the bottles cracked more easily now a year on. I've since resorted to adding 10% salt to each container to enable them to cool more without the expansion problems.

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PostPosted: Nov 16th, '17, 19:54 
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If you are wondering about cooling your FT with ice, this topic is worth reading:
viewtopic.php?f=11&t=26563&hilit=laws+of+thermodynamics

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PostPosted: Nov 16th, '17, 20:45 
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Hi all,

well here you go - YOU got the experience!

I forgot about the grow beds! Evap-cooling was more a "experimental suggestion"

So - mainly it is about "Keep direct sun away from anything where the water touches!"

[So - DWCs are about optimum for hot areas, if they are wood and can be painted white...]

thjakits

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PostPosted: Nov 17th, '17, 02:54 
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PLJ, I think your polystyrene/styrofoam would break down very quickly with the UV, a few years ago I setup a hydroponic system using polystyrene boxes from the local greengrocer and filled them with scoria, the sun broke them down within 12 - 18 months. The heat from the scoria exposed to the sun probably speed the process up a bit, your water wouldn't get anywhere near as hot as the scoria so you should get a bit more duration out of them.

You might be OK painting them white, but raw exposed to the sun I don't think they would last, you see some polystyrene signage around on buildings and it hasn't lasted too long even painted. The polystyrene signage would last a bit longer than my veggie boxes did because it's painted, but it still breaks down.

I think "Sisalation" would a better option, you would only need to cover the area exposed to the sun and reflect the heat away. It's not cheap, but cheap enough to insulate whole houses. Even using Sisalation who knows how long it would last expose to the sun. :think:

Last week my RFF & MBBF were that hot to touch you couldn't hold your hand on them for any length of time so I covered them both in Sisalation and it fixed the problem.

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PostPosted: Nov 17th, '17, 14:29 
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I thank you all for your ideas, suggestions and experiences.

Something that is not particularly well known, and which I don't think I've previously mentioned, is that Rainbow Trout (Oncorhynchus mykiss) bred in Western Australia have a higher heat tolerance than this same species when grown elsewhere, although I believe South Australian bred rainbows exhibit this heat tolerance as well, but to a lesser degree. This has occurred through natural selection over a hundred or more generations.

Whilst this helps growers of trout in WA, it in no way devalues any advice concerning the keeping of trout farther into summer. It simply means that we West Aussies have a little advantage in our corner in that we have a 1-2 ºC head-start with temperature mitigation measures. :)

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PostPosted: Nov 17th, '17, 23:01 
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Thanks for all this information every one. I noticed that about Rainbows as well. I wish there was more variety available here. We'll grow Rainbow Trout someday. It is important to look at as many parameters as we can to balance our systems.

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PostPosted: Nov 18th, '17, 04:17 
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PLJ I can remember reading a while back that you guys had a more temperature tolerant and faster growing breed of Rainbow Trout in W.A., a highbred species breed at the Pemberton Freshwater Research Centre.

The Pemberton Freshwater Research Centre (PFRC) is the largest freshwater hatchery and research facility in Western Australia. Located on the Lefroy Brook in Pemberton, the current hatchery site contains 10 earthen ponds, 22 concrete ponds and 36 research tanks fish hatching and larval rearing troughs.

Since 1971, we have managed the PFRC, originally established to produce trout to support the south west region's freshwater recreational fishery. Faster-growing sterile triploid trout are produced at the centre and a unique genetic line of temperature-tolerant rainbow trout that has attracted the attention of international research institutions.

http://www.fish.wa.gov.au/Sustainabilit ... ities.aspx

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PostPosted: Nov 19th, '17, 20:04 
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They're the ones, Joblow!

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PostPosted: Nov 19th, '17, 20:36 
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I harvested some beetroot yesterday.
Attachment:
AP beet.jpg
AP beet.jpg [ 257.55 KiB | Viewed 503 times ]
Perhaps I should have harvested it earlier because the leaves were starting to become a little droopy as though the plants were heat-stressed. Judging by the dirty colour of the roots I suspect the grow-bed media is overloaded with solids.

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PostPosted: Nov 19th, '17, 21:16 
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I harvested some trout yesterday.
Attachment:
Brown v Rainbow.jpg
Brown v Rainbow.jpg [ 253.87 KiB | Viewed 478 times ]
Pick the odd man out!
The brown trout (Salmo trutta) weighed 167g whereas the rainbows of the same age weigh between 400 and 500g.
At least I finally have the opportunity to cook and eat one in order to compare it with rainbow trout.

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