Backyard Aquaponics
A place to discuss aquaponics

A larger overall volume of water can help mitigate temperature swings from the heat exchange effect of flood and drain media beds or towers.
Example my Media bed system with a very large amount of flood and drain media beds compared to the amount of water in fish and sump tanks has a wider temperature swing on a daily basis compared to my system that doesn't have any flood and drain media beds and is mostly raft beds. In the morning when I feed the media system will be at least a degree cooler than the Raft system and then at evening feed the media system is at least a degree or two warmer than the raft system during nice fall weather when the day temps are warm and night temps cool off.

Having your GBs and FT inside will result in much more stable temps Brian, exposure to direct sunlight is the main cause of heat gain, just having hot air around the GB not so much, but the more GBs you have, the more energy will be gained.
The GBs are heat exchangers, not heat sinks. The Earth around the FT or any other components is a heat sink. You really do need to log your water temps to see what sort of range you are getting.
I rarely see mroe than 2C range in the day ATM with this system, but when the nights are warm, the drop overnight isnt as great as the gain during the day, so the water temp ratchets upwards over the days.
Forecast now is for 36C on Thursday and 39C on Friday, so I definitely need to get the trout out before then- maybe I'll aim for 40 or more today.

Another healthy looking one died overnight, 559g, which will be eaten for lunch. I suspect Zinc is the cause of the occasional deaths not related to the mysterious pop-eye that some have, as there is some water in the system that was from the galvanised water tank on the shed. I've ordered a good quality Zinc test at great expense (over $300, but the least expensive that was available).

There only appears to be one small fish in the tank, the lone Murray Cod, I doubt it is even 200g, after
almost 2 years in there.

"The GBs are heat exchangers, not heat sinks." of course they are, my mistake. Thanks for the important clarification.

We took 45 out of the tank yesterday, 3 eaten for lunch and the rest in the freezer, apart from the ~400g one I put into the large system.
There should be about 45 trout left in the FT, and I'll probably put most of them in the large system with the chiller, as the freezers are a bit full now and there is a heat wave on the way. Plus I've had more than enough fish blood and guts to last me for a while

Largest so far was 35cm, 716g, which would be quite a large meal for one person!

Only comment.. I seem to remember that typical detectability of test kits is above some of the suggested LC50 values..
Ie.. you can read NO ZINC and still have deaths

Trying to keep up with so much detail needs a younger mind...
..
.

This test kit is to the standard used on town water supplies, so should be good to test to quite low levels.

Yesterday's trout on the BBQ:



An of lunch from AP:

Yumsters.

Too late to help probably but there are labs that do water testing for agriculture that will do a whole battery of water tests for around $30-$50 USD. I'm sure there are similar companies in OZ.
The company I sent my samples off to last time also tests for copper and zinc in their W1 irrigation water test for $40 and sent me the results by PDF within a week of them getting the sample.

I did think about sending samples away for testing, but I'll want to do a number of tests over time, of water in both systems and the stored water, so that would work out to be more expensive.

I'm confident that Zn is the only possible metal "contaminant", as the water I put in the AP doesn't pass through any copper pipe, its poly all the way. I'll offer to do tests for others at a cost under that of lab tests, to recoup some of the cost. I'm told its a 3 week delivery time, as it isn't kept in stock.

..
And consensus seems to point. to my dramatic losses being Zn,
and the proven problem seems to be that the fix is not all that easy..
Part water changes did not help.. complete changes did not stop the problem..
There seems to be a mechanism by which the Zn levels are stored in media and get to a tipping point with lethal results..

I wish there was a way of chelating the stuff from a system.. you can't afford to throw out hundreds of Ltrs. Of clay..

Again... my death system works fine for Koi and yabbies ..

PS.. there was a bit of discussion on fixes in this thread..

viewtopic.php?f=1&t=22530&p=468003&hilit=zinc+removal#p468003

Given the amount of Zinc in the environment, it would be good to find an effective first-aide treatment..

CUPRISORB seems to read well as a potential fix, and can be re-activated with HcL
.

I contacted a recommended.local facility and they quoted about $100 per substance tested for, and when you are seeking an unknown, then how many do you test for.. just a stupid proposition ...

PS.. and GG .... I am planning a standby/backup Air-Supply and have considered that a single pressure switch could work with a relay.
To me, the biggest fear is partial pump failure.. ie.. with one pump feeding many locations, then a significant mechanical failure could leave sufficient pressure at the sender end and insufficient flow at the working end..
It would be better to have the pressure sender at the working end, and a cable back to the pump (in my case, back in the garage)
My thinking is for a control unit with push button..
PRESS and the main pump starts and the Sensor locks it in, but if the pressure drops, the relay drops and connects the backup..
Thus a power failure will cause change over as well as pressure failure, and if it s the power that failed, then you will know of the failure and reset by pressing the START again.

The only remaining issue is if you have gone away, and fall-over has happened..
But in my case the battery backup will be a UPS, which will be reporters by the mains

I think that philosophy is practical..

I'm planning to make it as simple as possible- the 230V pump is always on, with a drop in pressure turning the 12V pump on, either directly if pressure switch contacts are NO (preferred), or via a relay if NC. 150AH 12V battery will be charged by an independent PV panel, and with 3A@12V, it should run indefinitely, even in cloudy weather, with a couple of old 80W 36 cell panels. I might put a timer on so the 12V pump comes on part of the time anyway, at least for summer when DO is lower.
If I could find some suitable fish-safe electrodes, I'd also use a panel or 2 to produce Oxygen via electrolysis during the day as well.

Well, might need to do a bit more searching for labs. You want to find one that works with agriculture.
Here is the Lab I've used
http://www.agroservicesinternational.com
The W1 test for irrigation water includes;
Ammonium nitrogen, phosphorus,
potassium, sodium, calcium,
magnesium, sulfate sulfur, boron,
copper, iron, manganese, zinc, chloride,
electrical conductivity, pH, carbonate,
bicarbonate.
And costs $40.00 USD
Granted shipping would get a bit costly for you guys to use this lab but they do work with overseas accounts.
I'm sure there have to be some other labs around the world though that do this sort of testing for similar prices.

A couple of quick thoughts.

Zn: lc50 for fish is very low for multiple metals, Hg, Cd, Cu, Zn, Mn, Ni, Al, (in approximately that order) and others. Note that some of these are frequent in stainless steel. Stainless will leach under the wrong circumstances, notably if it is in an oxygen depleted (reducing) environment. Strong chlorides also tend to be hard on stainless, in my experience (HCl is a no no in stainless).
There are commercial ion exchange resins that will remove these form solution, but I do not know where they would be available to you. These resins are also usually regenerated with hcl. I was surprised to see reports that the lc50 for iron was just over double that of zinc for the study I saw (not trout). Presumably the Chelates are different. For removal, EDTA is sometimes available by itself, and should chelate most metals, I think. Clay could possibly be stripped of metals by circulating an HCl Sol'n and then purging. Most chloride salts are soluble.

Gordon, for your electrolysis, think carbon. I used to (as a kid) pull the (carbon rod) center electrodes out of D cells for precisely this use. I've launched (and lit) more than a few hydrogen balloons.