Backyard Aquaponics
A place to discuss aquaponics

Hi awesome community members,

So now that we are past the winter solstice I have been keenly looking forward to spring, warmer water temps, and faster fish growth. But an unexpected dark cloud has arrived - my lovely silvers have started dying! In the last fortnight I have pulled out about 10 dead fish, one or two at a time.

Water temps have been steady between 15 and 17 degrees C over winter, and for the last fortnight 16-17 degrees.
Nil Ammonia, nil Nitrite, Nitrate about 40, PH 6.5. Oxygenation has been good (I assume) as there are two pumps on timers and they run on a cycle all day and night.

The water is shared between the two tanks via cross pumping and water bridge, and the mature jades (~550gm) in the other tank have been fine.

Summary of my system in here: http://www.backyardaquaponics.com/forum/viewtopic.php?f=18&t=13992&hilit=tallman.

Here's a couple of photos of the fella I just pulled out. It's 17cm long, has a nice slime, no visible lesions or growths, bright eyes, light pink gills.

I'm stumped! Any thoughts very welcome. Thank you.

I would first salt to 3 ppt, which is 1 kg pure salt to 1000 litres of water. Take into consideration the volume of both tanks, grow beds and sump if using one. Split the salt between the two tanks would be best.

Don't gaping mouths normally mean a DO problem? Pumps don't automatically produce DO, so maybe add a venturi or get an air pump to help out? Maybe they have outgrown the limited amount of O2 coming in on the flow?

Have I got your system right...

You pump from both fish tanks... one with x number of Jades.. the other with about 20 Silver Perch

Tanks are joined by a "water bridge"... pumps are activated at different times... presumably drawing water through the bridge from one tank to another?

The grow beds appear to drain individually to the fish tank from which they're pumped?

What's the purpose of the bridge?.... especially as you once had two separate systems??

Often that is the case but you find that the larger fish always die first if there is a DO issue and the fact that his larger Jades are in the same water with no problems could probably discount this.

ccBear, thanks, I'll get same salt and get it into the tanks.

Hi Rupert, each tank has a pump and each pump feeds into both GB's, and the pumps alternate. So when the pump in FT1 is on it is draining water from FT1 and pumping it into GB1 (which drains into FT1) and GB2 (which drains into FT2), so without the bridge FT2 would overflow. And vice versa when the pump in FT2 is on. The point of this setup is to ensure that in the case of a pump failure both GB's are still filled periodically and both FT's are still aerated (even if half as often) during the time it takes me to realize I've lost a pump and replace it.

There is also a small air pump feeding both tanks as a supplementary air supply, but it certainly wouldn't be enough on it's own.

Thanks again.

How many Jades are in fish tank 1?

10 Jades in FT1 mate. Nice big fat fellas.