Backyard Aquaponics
A place to discuss aquaponics

Hi to all out there i am a newbie from Tasmania and were wondering what fish besides trout would i be able to raise in Northern Tasmania ?? or am i reduced to goldfish ? Would love any thoughts?
Mark

Hi,

I'm in NW Tas near Devonport and have set up a system at the school I teach at and have had nothing but trouble with trout (triploid rainbows). I lost my last one today when the water in the main pond reached 31 degrees despite being covered and protected from the sun. I'm not going back to trout. Over the last few days I've been in contact with Tim Farrell, senior fisheries officer at Inland Fisheries, to acquire a permit to go out and catch freshwater blackfish starter stock (about 20-30 fish) which has a far greater tolerance to warm water and are not worried about the cold during winter. In my system they need to be able to cope with water up to 31 degrees in Summer right down to 2-3 degrees in the winter. They can tolerate a lower DO level as well and grow to a descent size. The trick will be getting the wild caught ones to convert to aquaculture pellets. The fry won't be any trouble getting them to eat commercially prepared foods. Apparently Tim is trialling some blackfish down at New Norfolk at Fisheries right now to assess their suitability as an aquaculture subject. The great thing about the freshwater blackfish is that it is possible to breed them yourself making stock replacement a snap. Here is an article on the breeding of Gadopsis marmoratus: http://www.sardi.sa.gov.au/__data/asset ... _Basin.pdf .

The way I am going to do it is to keep 20-30 adult fish in the main fish tank and then in mid spring fish out two pairs (sexing them using the backlighting method described in the article + venting) and place them in a 2000L pond I have with 90mm pvc pipes stacked on the bottom with a plastic coated flyscreen insert in them so that the eggs can be laid on the insert and removed for hatching in the fry tank I have (as described in the article). I don't know how quickly they grow yet but when the fry are about 5cm I'll harvest the adults and release the fry into the main grow-out tank. From what I have heard so far they can be kept at relatively high stocking rates as well without too much aggression. The 20 goldfish I have in the sumps away from the trout are no problem down here and survive anything. It's useful to keep a few around as a fail-safe in case something happens to the rest of your fish. I'm sure my system would have failed if it wasn't for the goldies in the sumps. A friend of mine has blackfish breeding in his farm dams so this is where I'm going to acquire starter stock once my permit has been approved so they don't need to be taken from the rivers.

It's a pity that relocating redfin perch is illegal down here as you could probaby catch as many as you need for your system from some of the rivers up around here. Tench can be caught as well (esp. near Deloraine) but fall into the same category and I don't know whether they are much of a table fish (think carp).

31 is way to hot for Trout. They should have been pulled out well before your water temp gets there.

They are pretty easy fish if you stock to the amount of filtration you have, supply air, dont over feed (to your filtration levels) and dont try to keep them in water over 25 for long periods of time.

How on earth did your pond get to 31 degrees...

I've struggled to get my system up to 25 this summer...

I know 31 is way too hot for trout. I've kept trout in other systems for many years. I do supply aeration and have 2800L of filtration volume by way of 4 x 700L growbeds for about 3500L of water combined with 2 x 5000L/hr pumps to circulate the system. I'm aware of these issues.

The grow-out tank is under cover but three of the four grow-beds receive full sun for 1/2-3/4 of the day. They are fully covered as well but the sun still reaches them as it moved across the sky. We had reduced the plant load over the holidays and these have acted like giant heatsinks. We don't overfeed the fish. Over the holidays we were feeding them every three days as we had to travel 30km into work to look after them. The system is a flood-and-drain system and the beds in the sun (with clay and gravel media) got hot during the drain cycles and have been heating the water at the same time. I can reduce the flood-drain cycling time and this might help minimise the beds heating up as they have been. Our summer has been very hot and dry. Most days have been over 30 degrees during the January break and it rained only twice in 8 weeks. I built the system back in January last year whilst our new science-centre was being built around it (we applied for and got a grant for $1.8mill. to build a biotechnology lab and I was successful in getting a large aquaponics system included in the build). In their wisdom, the builders that constructed our aquaponics compound then backfilled around my two 700L sumps with 30cm of blue-metal that also sits in the sun getting really hot. This radiates heat directly back into the sumps with which they are in direct contact. I have balance-pipes running under the gravel between the sumps and this is also being heated by the hot-rocks on top of them. The OH&S committee at the school would not allow me to have the pipes left exposed to the air so 30cm of blue-metal was dumped over them to conceal them and so remove the risk of tripping.

So, you see, there are many compounding factors that I need to contend with and I could persist bloody-mindedly with the trout, which do fantastically from autumn to spring (as well as jump through all the hoops I have to with fisheries just to be allowed to keep them) or I can replace them with something that has wider environmental tolerances, is native to the area, and which I can even breed myself (I teach marine science and have been breeding fish for 30 years), to add to the educational value of the whole system. So, the trout are out and I'll be trialling the blackfish in cooperation with inland fisheries to determine how successful they will be under aquaculture conditions.

Please let us know how this trial goes...

Would love to see a photo of your system there Tasv.

Sounds like an interesting project though that article does say that the fish became stressed at 26 - 27C and in other references I have it says that the blackfish only survives 5 - 28C so if your temps range from 2 - 31 you may still have problems.

Hey TasV, you said that you Flood and Drain and that your Tank has gotten to 31deg C..

Have you ever thought of a Difference Process.. Constant Flood during the heat of the day.. therefore your not drawing hot air into the growbed..
-- Sorry I think that was the mistake you did..

Have the system Drain during the night if you want to flood and drain..

I think if you changed how you handle your growbeds you should be able to control your temperature's..

Can you shade the whole system

Juergen

Rupert, I wish I had known you were a distributor of BYP aquaponics systems 2 years ago! I've been a member of this forum for many years and stopped coming here for a while because there just wasn't enough hours in the day and the build of our science centre was getting really full-on. I came back the other day, but could not remember my log in details so I made a new account, hoping to pick people's brains about controlling the heat better (though in all fairness it's really only a problem for about 2 months and one of those months is over the Christmas break so I should try to manage the system by harvesting all the fish before we leave and just leave the goldies in the sump to keep things ticking over until we get back in early Feb). When we started the planning of the setup I said I wanted a BYP system and gave them all the information. Originally I told them to just buy me the bits and I'll put it all together the way I want but they would only buy off-the-shelf packages and then refused to buy a system that had to be shipped from WA. So, they told me they were buying a Practical Aquaponics system from QLD instead to save on shipping costs. If I had of known there was a NSW distributor I would have pushed the issue a bit harder. The system is good, but I had to modify it significantly to do what I wanted it to do (due to missing parts) and I liked the stand setup that the BYP systems have to support the growbeds... oh well!

Hi Faye I was due to replant the growbeds in the next few days so will try and take some photos over the coming week. My next job is to work out how to get a hose to my float-valve attached to the satisfaction of the OH&S people so that top-ups can be automated. I'm going to have to bury it or run it up and over the cover. I can't believe the amount of evaporation I'm getting!

This is the system as we were putting it together 12 months ago before the fence around it was added, the pumps installed, and the media and gravel floor was added. Some year 9 kids from my marine science class and I put it together. Even with the fence around it and the security camera on it we have still had trouble with people breaking in and breaking things. We were building this system whilst the building around us was being built. It's now all up and running with some very cool resources for the kids. We have a biotech lab where we can do things like tissue culture and DNA investigations, a large saltwater reef tank, a weather station on the top of our outdoor classroom, a 4kW helical wind turbine, solar panels (still to be installed... we just won a $50,000 grant to have these installed) and solar hot water systems, a greenhouse, a bush tucker garden and lot of veggie beds along with a wetland area (that didn't work out like we planned after the contractors 'interpretted' the plans) .The whole building is built around energy efficiency principles but the practicalities of it are that in summer it is a hothouse!

From What source are you going to be topping up the system..??

Main Water or Tank Water..

the reason I'm asking is if by any chance the water company's change or have had to add chlorimine to the water as they have done pipe work in the area.

I would not want to know that all the hard work of growing the fish is Lost due to Top up Water..

Juergen

2 x 10,000L rainwater tanks with a pressure pump attached to the taps.

If you running off tanks.. Would not it be easy to take the pipe up over the top..[To the under roof line] and drop down where it is needed..
- also insulate the pipe so it does not get to warm sitting still..

Other wise scrape back the blue stone.. run the drop a feed pipe into the trench and Back fill it..

Just a suggestion..

Juergen

On the temp thing. My big system is under 70% shade cloth and is constant flood and its got to 32C a couple of times this summer. The silvers go nuts at feeding time at this temp

That's why I said