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Grubs

Dealing with excessive heat in small ponds

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Just wondering what innovative ways people might use to cool ponds if too hot. Sprays? bubblers? fans? paddle wheels?

I'm in Melbourne but I'm establishing some 1000-3000 litre above ground "ponds" in a glasshouse.

(stock troughs, aquaculture ponds).

I can insulate the sides heavily (e.g. rockwool or fill around them with sand to make them "below ground" to minimise temperature fluctuations which in a glasshouse are huge.

On a run of 40C days I had some 200l black tubs exceed 45C water temperature (no livestock). Air temp in the glasshouse (with doors open) can hit 70C at the worst for a couple of hours - but this isn't sustained and most nights are ~20-30 but the water holds onto the heat.

The larger the body of water.. the lower the temperature increase each day, but I think I'll need sprays, or fountains or something to cool the ponds down at night a bit so then next hot day isn't compounding the heat problem.

In Melbourne this happens maybe for 1-2 weeks in summer only.

..so apart from refrigerated chillers and bags of ice - what works best to cool things down?

Edited by Grubs

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Evaporative cooling. Most glass house suppliers have ready made units . essentially trickling water over high surface area undet a fan. I would also increase dissolved oxygen level in ponds too. And if your able to shade the glass house then even better.

If you have a larger 20, 000l plus rain tank nearby then connecting your small tubs centrally will help.

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Yes but covering water surface with floating plants can also decrease area for oxygen exchange. On hot days this is a problem.

Grubs - I don't know what your budget is but a very efficient solution is to run some air lines of pure oxygen to each pond. If your able to maintain dissolved oxygen levels the livestock can temporarily handle very high water temps. A large oxygen cylinder will last several weeks easily if slow trickled out via airstones. All live food fish transporters use oxygen and they are able to carry more fish than water this way.

Edited by aquaholic99

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If you cover half the surface with plants, you get a water movement effect, as shaded water sinks and drags accross the hot water.

This convection current can actually increase oxygen levels.......... although this is only noticable at rather low stocking levels.......... and usually only in ponds that are exposed to sunlight.

Oxygen is certainly at the centre of the issue, and having some in cylinder form available for the hottest days is definitely an elegant solution.

Its going to be hard to actually cool water inside a green house......... although being able to exchange water with a large in the ground rainwater tank is a very clever solution for it too.

Winston threads ftw

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Good idea to concentrate on cooling the glasshouse first - I was fixated on the ponds.

I might try an industrial fan with some misters in front of it like they use at the tennis as a first step and see how it goes.

For context - the glasshouse is 14m x 7m and 4.5m high at the peak built on the northern side of a big shed (so its pretty big). There is a small but powerful 14" industrial fan set up to blow hot glasshouse air into the shed to heat the shed in winter but I've never really used it... so I can move that fan to an outer wall of the glasshouse. The gables(?) on each end are colourbond sheeting so I can mount the fan on those to blow outside air IN and then rig up some misters in the air stream. A waterproof thermostat could automate the whole thing. The heat from this summer is gone in Melbourne this year I think so I have 10 months or so to engineer it.

O2 isnt an impossibility - My account with supergas is open for the CO2 I put in planted tanks and I have the regulators etc. The gas is cheap - its the bottle rental thats the killer!

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My university workplace has a road full of glass houses of similar size. They have outer shademesh on rollers for rooftop shading and evaporative coolers on the windward side, designed to create a heat gradient with vents at the apex and leeward side. It's a fairly standard and proven design. To cool within they use water misters which also water plants. Almost all glasshouses have a wide door at one end and a narrow door/window at the other for a natural venturi of fresh air.

If you can keep the heat out and also cool the air within and then cool the ponds and maintain dissolved oxygen then you have a pretty good plan. The oxygen bottle is a good safety net. You only need one regulator and one cylinder if you can run a mainline. (oxygen having a different regulator than CO2).

Plan B would be to have somewhere safe to move the fish if it's only for a couple of weeks.

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