Backyard Aquaponics
A place to discuss aquaponics

look for the book "small scale aquaculture" by dr. steven van gorder...he just released a second edition
i recently got the book, and have only had a little time to look it over, but there are some concrete tanks in it

Thanks, Keith - that book title sounds particularly relevant to my situation, especially if concrete tanks are discussed in any sort of detail. I will look it up first opportunity I get.

PLJ

I am trying to set up a biofilter that I can retrofit to my large trout tank before they get too much bigger. Below is an overview plan of the tank site with an indication of what I am hoping to do. Before installing the filter, pipe work and pump I want to get an idea of whether or not it is feasible in broad terms. There is every chance I am unwittingly about to transgress a cardinal rule of fish keeping or pond filtration so would greatly appreciate some feedback.

If the pump sits alongside the outlet of the biofilter then it will need to pump upwards about 3m to return the filtered water to the tank.
Originally I planned to have a submersible pump pushing water up to the drum biofilter mounted at the rim of the tank, thus only requiring gravity for it to fall back into the tank. Then I thought that with a slotted pipe across the flat floor of the tank I would be better able to remove 'solids', especially if I developed some circular flow with the return water.
Will the biofilter operate well enough with gravity fed water?

Well, my question remains unanswered so I plan to proceed with the retrofitting of a gravity fed biofilter and solids drain, with pump return to the tank.
The tank currently supports a large, floating mass of azolla (Azolla pinnata), which is thriving. I plan to replace much of the azolla with leaf vegetables on rafts, probably bamboo rafts like my son made as a trial for another thread.
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It wasn't my intention but it seems I will be getting into DWC before I establish a single grow bed.
I will document my progress in a member's system thread.

They grow so quick don't they PLJ? How many do you have?

They do indeed, Faye, and it is very exciting to watch it happen. The frenzied way in which they feed is very entertaining and my kids and I enjoy two or three 'showers' from them each day. We also peer over the edge of the big tank and watch them scoff moths at night.
I had 100 to start with but lost four over a few days back in mid May. There were a lot of bees landing on the tank surface, back then, and I wondered if a bee could sting a trout as it was swallowed and, if so, if it could be fatal to the trout as well as the bee. Someone may know.

Did you cut them open and see if they had swallowed a bee?

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That would be logical, Faye, but it was only afterwards that I wondered about it since, at the time, I was half expecting a mass die-off for a host of other reasons as predicted by all and sundry at the beginning of this thread.
If I have another death then I will put on my mortician's hat for certain.

Welcome! And enjoy experimenting! It is a great way to learn provided it is not too frivolous and it sounds like you have put some thought and effort into it, so well done.

We have been growing fish in our concrete swimming pool for 4 1/2 years now, we certainly made mistakes early on, but learnt a lot. It is well worth the journey.

My only 'suggestion' would be that catching trout on a line is fantastic.......for the first 15-20 , then the 'smart ones' catch on and avoid it. We ended up having to drag net.....but our pool is only 10,000 litres.

We now have perch in there, so it really doesn't matter how long they stay.

Good luck, and enjoy!

Thanks, dandm. I read through your system thread and learnt a lot. Catching the trout at harvest time is a challenge I look forward to and am confident I will get it done, since I am sure I will have no shortage of volunteers to assist. The use of a prawn drag net is my back up plan.