Backyard Aquaponics
A place to discuss aquaponics

Back on or around 18 Dec when I scooped out the last of my Rainbow Trout (dead and alive), after failing to keep my tank water sufficiently cool to sustain their lives, my records indicated that I had removed 298/300 fish. I assumed that the two unaccounted for fish had died previously and their carcasses lost in my large body of water. I was wrong.

Last Thursday I discovered a floater in my big tank which, on closer inspection, was identified as a trout. I had to be sure since I have some sizeable Goldfish in there, as well as a few Silver Perch. Again on Friday I found a dead trout, so all 300 fish are now accounted for. Interestingly, these two tough RTs survived way beyond the point where the last twenty or so fish succumbed to the heat a month earlier. It is a shame they couldn't have been breeders since they clearly had an evolutionary edge over their siblings as far as heat tolerance is concerned.

My theory for why these two finally went fins up is that I may have interfered with a cool spot that they had found in the depths of the tank. During a scheduled power outage on Tuesday I ran my generator to keep the pumps going. I powered up a third pump that I haven't run since the final trout harvest, simply because it was going to cost nothing since the generator was running anyway, and it had spare capacity. This pump lifts water from the bottom of the tank to the surface, providing some aeration and assisting with a gentle vortex. No doubt it also evens out the temperature of the water, ie removes thermoclines, thus destroying the cool safe haven that the two surviving trout must had occupied during their month long battle against the odds.

In summary, it was a goal of mine to take some of my Rainbow Trout through into the new year, and it is now apparent that I have inadvertently managed to achieve that. It is a hollow and probably pointless achievement. I have to ask myself what is the point of extending the season for the trout, other than just for the sake of it? As far as I know, these last two trout haven't eaten since the water temperature rose above an acceptable level for them, so there would be no weight gain advantage for me. About the only advantage that I can determine is if I could keep them going long enough to see in the cooler weather of autumn, at which time they may have started feeding again, then they could have gained weight. Also, if I planned to attempt a trout breeding exercise I would need to take the fish through to another season but this wasn't the case.

This season I will apply the lessons learned from last season's mistakes and folly and aim to have all RTs harvested by no later than the second week of December, regardless. I just need to devise a method of capturing the buggers when I need to!

I think the experiment was well worth it and wow, how close too. Two/three months and it would have been trout season again. You guys have really copped the weather though this summer so I am not surprised you lost the last few. Thanks for the update, PJL.

PLJ have been following your thread for many months now with interest as I have many unutilised concrete water tanks on the farm here. Would it be worth trying Murray Cod with silvers? Murray Hallam is also advocating the use of a pleco or two in the mix to manage algae issues.

Santalum, I would very much like to try my hand at Murray Cod (Maccullochella peelii). I had a mate who studied aquaculture for years and researched fish species for their suitability in a range of systems. His final conclusion was that Murray Cod, or Goodoo as he liked to call it, was the best species available in Australia for fresh water aquaculture. His research was done in the ACT so that fact may have influenced his analysis.

For the time being I have my hands full with Silver Perch, Goldfish, Rainbow Trout (in season), Marron and Yabbies. If the opportunity presents itself down the track, however, I will be in like Flynn to get some 'Goodoo'.

The only problem I have with algae is the lumps it forms in the GBs. Even the string algae in my big tank didn't appear to bother the RTs at all. It was either a sharpened, short handled screwdriver through the brain or a hot December bath that killed that lot.

I would be happy to have some catfish swimming around with the other fish but my problem is that I can't see any fish in my tanks unless they break the surface when feeding, or they come out on a hook or in a net. Unless I completely drained any tank in which I had catfish I wouldn't know if they were still kickin' from one year to the next.

Hhmmm, perhaps a light mounted to an underwater camera like Mantis has.

Underwater lights that can be switched on to see what's what way down there? Or, now that I think about it, is the tank too deep to see that far?

Sharing your experiences are appreciated, thank you.

It's not so much the depth of the tank as the colour of the water - it's like strong tea, largely due to tannins. If the water was clear then even down at 2m depth I'm sure the visibility would be good. The Puddle Princess took a plunge in my big concrete tank last season (fetching a missing thermometer, as I recall) and was armed with a proper underwater diving light. She abandoned it, saying that it was totally useless in the brown water.

For weeks I have been trying to scoop up Silver Perch from my lower pond but they have proved elusive, even when they are feeding at the surface. I have managed to catch just two small ones but my records indicate that there are 26 second year fish and 60 that went in as fry last May. I have needed to catch some of these SP since I need more mouths to feed in my AP system in order to keep the vegies going well.

My GB plants are starting to look a bit hungry because they have used up the nutrient provided previously by the now defunct Rainbow Trout population. Since the trout exodus I have been feeding only small amounts of feed to the five small Silver Perch and dozen or so Goldfish that are currently in residence in my big concrete tank. I am still picking many tomatoes, capsicums and chillies each day but the desired plant vigour has started to wane.

Anyway, yesterday I brought out the heavy artillery and used it on the Silvers. The young bloke and I worked a prawn drag net along one side of the pond (it is 16m x 8m), stopping and emptying the catch after each of five drags. We caught 41 Silver Perch in total and promptly transferred them to the big concrete tank to power the GBs. Some of them were a decent size, too, despite having no supplementary filtration or aeration in their pond.

They are a good size, PJ. Did you drag anything else out of the pond besides the SP whilst 'prawning'?

That is a good question, Charlie. To be honest, I didn't really want to wade in the pond barefooted because one never knows what can find its way into a pond like that. Surprisingly, I felt nothing but clean concrete under my feet and a few fish brushing against my legs. All that I found in the sock of the drag net were the Silver Perch already mentioned, five bamboo leaves, two grass stalks and a single yabby. Since I only put three yabbies in the pond to start with, catching just one is fair and reasonable, I reckon, especially since we dragged the same side every time.

This morning the big Silvers were hitting the 7mm trout feed (about all I have right now) hard, despite their tangled net ordeal just yesterday arvo.

Wet sleeves PLJ, wet sleeves.

Haha, well done Ron, well done! Not bad for a landlubber, anyway...

Hi PJ, read your whole thread over the last few days. Was a marathon session but really enjoyed it. Thanks for sharing all your adventures in AP, it is very much appreciated.

Regards, Martin.

I'm glad you enjoyed reading through my thread, Martin, and hopefully have learned from some of my mistakes. I feel honoured that you committed so much of your time to my AP story.
Cheers.

I enlisted the help of the Puddle Princess to help me drag the prawn net through the Silver Perch Pond, today. She was a fast learner and we caught 12 SPs in 10 minutes, including five good sized ones. The fish were transferred to the trout tank without incident. There are now 58 Silvers in the tank, plus about 13 Goldfish.

It is interesting that the Goldies that grew alongside last years Rainbow Trout seem to attack their food aggressively and are very fast swimming, at least in comparison to their siblings in another pond. Their rate of growth, too, is very trout-like.

Hi PJ, definitely learned a thing or two but must say there weren't too many mistakes and you've had some good harvests too.

I was thinking maybe the goldfish are taking on trout traits to fit in, like a form of camo: "I'm not a goldfish I'm a trout!".