Backyard Aquaponics
A place to discuss aquaponics

I want to run some rainbow trout year round in my AP. It has run a full year with silver perch and never really got warm enough last year for planned barrumundi. I found it difficult to drive my plants with silver perch not the best feeders in the colder days.

I maxed at 26-7C for a few hours on the hottest of days and would expect it to have been cooler at the bottom of my biggest grow tank buried 1.8m deep. Since last summer will also use more shade and a air blower at the hottest times.

My question is in peoples experience do smaller or larger fish tolerate higher temps?

I can run some of my winter stock on or buy in some new young fish for the summer.

I have had trout over summer for a few years now and I am fairly confident that it is possible.I have friend that grows them out for sale and he claims that the small ones can take up to 30 c but the tolerance comes down as they get bigger but by that time the weather is cooling down an they are OK.I have had them for the last two summers and they have done well,I am now harvesting fish at 600 grams.This year I bought 47 in January and only lost 3 up to May.The first one died the day after getting them and the other 2 died at separate times when the weather wasn't hot.I have them in a tank outside the green house with a white cover over it and it is quite cool under it.I have a sheet of shade cloth over the tank which I can spray water on if it gets too hot but didn't need it.With bigger trout 26 is the upper limit and when they are heat stressed the they swim at the top of the tank so if you are thinking of harvesting them it is easy,if you put a net in they just swim into it.

Hi. I'm also thinking about how to keep trout longer into summer. A grow tank buried 1.8m deep sounds interesting and a good start to keeping a system cool, can you post some pics, give us a bit of a rundown on the system ? cheers.

Gday

This tread has my interest as I have run Rainbow Trout for the first time this winter & was wondering when to harvest them.
Ferguson springs http://www.fergusonsprings.com/Aquaponics/aquaponics.html Gives temp tolerances (Stressful Zone) as 4-26*c


dbird What size do you call bigger Trout ?
From my records my systems hottest water temps last year was 27.3*c
I guess when the Trout start to gasp at the surface its harvest time !

Cheers GTK

Sure it's possible to carry trout thru a summer here but is it worth the stress?
From my limited experience I have had both large and small trout go belly up in the heat. We get them >600gms in a season and >1kg in two seasons. The ability to remove heat plays a huge part and high humidity will reduce this ability if you're relying on evaporative cooling. It only takes 1 hot humid day to raise the water temp & ultimately lower DO to terminal levels.
I have carried trout thru summer the last two years and the veggies have suffered as a consequence.
Will I try again this year? Probably not, too much stress.
Having said that I would like to see what two summer trout would be like although I haven't seen it done here yet during my time on this forum.

Anything above three to four hundred grams I would worry about if they were in the green house.I have lost some big numbers of them a few years ago but since I have had the covered tank outside the GH I have stressed a bit while the trout swam around quite happy.I did have one that was too smart for me to catch it but I went out there one day when it was getting fairly warm and it was on top.when I put the net in it swam straight into it .That one was twelve hundred grams .One hot day is not a problem it is when you get a week of 35 c plus that you have a problem as it heats up a bit more each day.I am posting a picture of my bach up system which I didn't have to use last year .It sprays water onto the shade cloth to cool it .If I have to use it this year I might try running it at night as the water will be sprayed into cold air and it should start the day colder.If you start the day at 15 c you should be right but if you start at 23 c and it is going to be 40 plus you will be stressing before the fish are.

I have a photo with the spray running but cant down size it.The pipe you see in the middle has a slot in it and sprays onto the shade cloth.This should also add oxigen to the water.

Water running down the shade cloth looks like the best idea
Tank buried. When you pump the water to the grow bed it will take on heat
A blower or air pump running on a 40 deg day will only give more DO ,It is also putting 40 deg air into the water

That was largely my aim to get a more even nutrient load on the veg. I still carry my silver perch from stocking last summer, not big enough as yet to eat.

I also bought some Barra last summer but they have spent the winter indoors because my water was sitting too low in the AP for most of summer. I hoped i might be able to introduce them for the height of summer.

So I should be able to keep up the nutrient in higher temps, for the most part of summer my system stays within the tolerance of the trout. There was a few days last year when I pushed the 27 mark by afternoon for some hours. I was thinking some changes i could knock the edge off that temp those days.

My aim was to achieve some sort of continual stocking and feeding rather than a all or nothing approach. The idea to run a few trout over summer so the cooler days they are feeding well and the hotter days the silver perch. I can once the perch are large enough harvest a few and add some more on a ongoing basis.

Last year the perch stopped feeding and i had to wait till trout fry where available.... the veg suffered.



The pics i have are a bit old will get a new one and post latter today.

Dbird thanks for the info on fish size, I like the shade cloth idea. I have a spare temp controller that will turn on something on when temp hits the set level. I will have to consider something like that.



I agree, the blower I have has an attachment for a pipe on the inlet I could bury this under the bushes next to the system to cool the inlet in the shaded soil.

This is the AP as it stands now, the blue tank is near 2m deep 4500ltrs. I am light on grow beds still, have some new ones I am currently setting up now to install with the next increase in stocking density.

Milne you'd remember the old "Coolgardie Safe", this summer I plan to hang Hessian down into lengths of spouting filled with water along the full length of the system and around the fish tank. I could put a float valve on the spouting if the water was evaporating too quickly and have it connected to the hose or a water barrel.

The water in the spouting would wick up the Hessian far better than it would with shade cloth and if needed could have mist sprayed on it.

I'm currently pricing Hessian, the best price so far is $97.19 Hessian Roll - 1.83m x 50m, I'm hoping to get the price down on that if I can.

Shoot me down if you think I spinning my wheels

Hessian falls apart in the sun after a couple of years, I used to make bags from it for my cherry trees to stop the birds and fruit flies, but now use shade cloth. Costs more, but lasts much longer and is stronger, no noticeable degradation after a few spring-summers in the sun.

I like the bit about you would remember the cool Coolgardie safe are you saying I am old
I just remember them and sides was hessian but if I was doing it I would go for 1 or 2 layers of shade cloth
I wouldn't have it wicking just a constant trickle

That's why I am considering trying running the spray at night using a timer say between 1 am and 5 am so it is getting cool air on it so the temperature is a lot lower in the morning and takes longer to heat up .I find it is usually not the first hot day that kills the fish in a heat wave it is the fourth or fifth one because the water gets hotter each day.By having summer and winter trout you avoid the problem of too much nutrient and then none .I am also getting a bit excited about a seaweed solution that I am putting in the system but that is another subject.I will post something on that later.

Oceanarium, that tree you have in the background looks like a nice cool place to have a tank.