Backyard Aquaponics

fish dying i suspect from new food
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Author:  pdogg [ Feb 7th, '19, 11:35 ]
Post subject:  fish dying i suspect from new food

hi all,

My eel tailed catfish have been fine since i introduced them to the tank ~ 2 weeks ago.

I've been feeding them every few days with a beef heart and prawn mix (not too much yet to let them settle in, system is pretty new also).

So last night I fed them with the new 2mm aquaponic feed pellets I got and this morning three of the larger ones are dead.

My assumption is that the 2mm was too big for the ~5cm fingerlings. Does this sound plausible? Could they die from this?

A bit more system info below:

- Tank size 800L
- growing media 250L of expanded clay
- Number of fish 21 at 5 cm (will reduce this number to around 12 once they start getting bigger)
- pH 8.2
- Amonia, Nitrite, and Nitrate 0ppm

Any thoughts would be greatly appreciated!!

Author:  earthbound [ Feb 8th, '19, 11:21 ]
Post subject:  Re: fish dying i suspect from new food

pH is pretty high, there may have been a little spike in ammonia, this would affect them quite a lot at that Ph and I'm guessing being in SA your water is pretty worm as well. Were they eating?


Author:  pdogg [ Feb 9th, '19, 20:51 ]
Post subject:  Re: fish dying i suspect from new food

Thanks for the reply earthbound.

They were eating but I didn't check to see if they'd finished all the food so there may have been some left the water.

Can ammonia spike and then go back down to zero the following day? Because I checked the ammonia the next day after I found them dead and none was showing up.

I've read on another thread that catfish should be ok with the pellets so the only thing I thought could be an issue was the size?? I really have no idea but I'm very reluctant to feed them the pellets again until I work out whats going on!

Author:  mv1973 [ Feb 10th, '19, 05:02 ]
Post subject:  Re: fish dying i suspect from new food

Hi pdogg

I have about 120 eel-tailed catfish which I have had for about 3 weeks and have fed them on pellets ranging from 1mm up to 3mm and 3 different brands (they prefer sinking but will come to the surface for floating pellets). They always eat everything, I have only had a couple of deaths and that was because they jumped out of the tank (have netting on tank now). I have them in a Aquaculture system which was still cycling with ammonia at 0.25 and Nitrite at 0.5 but the ph is about 6.5 to 6.8, temp 26-28 (because I have Barra in the same system). I also keep the salt at about 1300ppm (obviously you wouldnt want to do that in Aquaponics).

Author:  earthbound [ Feb 10th, '19, 06:55 ]
Post subject:  Re: fish dying i suspect from new food

The Ammonia won't disappear overnight but the spike could have happened days before. Still, could be sooooo many different things, though unlikely to be feed.

Author:  pdogg [ Feb 10th, '19, 11:44 ]
Post subject:  Re: fish dying i suspect from new food

yeah just seemed like the feed was the issue as it was the only changed variable but perhaps just a coincidence...
I think ill just experiment with adding a little of the pellets and see what happens.

I imagine the pH will decrease as the system matures?

Thanks for your insight mv1973, its good to hear from others who have the catfish because I found it a bit harder to find information on them (they don't seem as common as other species). All the best with them!

Author:  mv1973 [ Feb 11th, '19, 04:13 ]
Post subject:  Re: fish dying i suspect from new food

I lost about 20 silver perch once for no known reason, all water parameters were fine and it was a mature system and no high temperatures. The only thing I could put it down to was a chance that I had handled poison before I fed my fish (or perhaps spray drift). I lost one the other day as well in that 47 degree day we had, water temp got over 30 degrees. I should have turned off the water to my grow beds, I now will be going for a split system to make this easier.

I hope any of this helps, I have found catfish extremely tough (except when they fall 1.2 metres onto a concrete floor).

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