Backyard Aquaponics
A place to discuss aquaponics

Hi All,

I have experimented with a back yard system (on and off) for a couple years incl. doing a fair amount of research on aquaponics (incl. getting every edition of the byap magazine).

A few months ago I erected a 50m polytunnel as a sort of pilot study into Commercial Aquaponics. So far I have two test systems set-up inside it:-

The first is a CHIFT-PIST system with a 5000 litre fish tank (currently stocked with 300 tilapia fingerlings) overflowing into ~ a bank of 5 gravel grow beds (1,250 litre volume) overflowing into ~ a 2,500 litre floating raft tank (the sump).

The second is a PIFT (pump in fish tank) system with a 12,000 litre fish tank (currently stocked with 1,000 tilapia fry), which pumps water up to a bank of 10 gravel grow beds (2,500 litre volume) which then drain back into the fish tank.

At the moment I have two burning questions:

Firstly, what is considered 'plate size' for harvesting a fish?

Secondly, can anyone advise me of the total volume of gravel grow bed filtration needed to handle 1000 tilapia when they are at harvest size incl. allowing for a floating raft system? I have seen the 'rules-of-thumb' which suggest a minimum of 1:1 (fish tank volume to gravel bed volume) but this seems excessive when dealing with large tank volumes...


I look forward to sharing on this forum and hopefully proving the commercial viability of aquaponics in the near future.

Hey HMR... Sounds like you have some impressive big systems there, nice work..

Generally a plate size fish is around 400-500g.

Second question not so simple to answer really.. Our normal recommendations here work to be around 100-125 fish for about 2000L of media beds, or roughly 8-9 sqm of growing area. Tilapia can handle a bit higher than that, so you could probably push to 150 fish with monitoring. 1000 is a lot of fish, but that's also a very large tank.. Have you got any pictures of your set up?

Welcome

Interesting choice of user name

What am I doing wrong?

When I try to attach an image to my reply, I get an error message saying: "The image must be at least 0 pixels wide, 0 pixels high and at most 800 pixels wide and 600 pixels high. The submitted image is 2048 pixels wide and 1536 pixels high."

Ok I obviously didn't read that properly the first time...

Here's a few pic's of my first system:

And here's a few pic's of my second system:

Thats what i thought too...

Is that algae still on the top of the water in that photo?

You really need to cover the top of your tank to stop it from happening again!

Thanks I like hold(ing) my rod...I mean my username too

The algae in the large tank (second system) is dead (I hope) and merely a sediment on the bottom which is in the process of being cleaned out.

The first system though - yep I have an algae problem! Despite having added 400ml of Tetra Algorem (expensive product) it has not been eradicated. The algae is not on the surface and only slightly on the sides of the tank, the bulk of it is in the water itself i.e. DARK green water... Any suggestions?

The Tilapia don't seem to mind it though.

Firstly. Don't waste any more money on products. To get rid of the algae remove any source of light from touching the water. Anything that is still Alice on the sides of the tanks is a good thing

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I think that... even with Tilapia... you will struggle to provide enough filtration for the amount of feed.. and number of fish... in both systems...

For the second system... I would suggest that you need to implement an RAS aquaculture approach... a drum filter at least... and possibly even a direct oxygen injection system... (certainly a backup module)...

Or expand you system to suit the fish load

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You'd need an aweful lot of bath tubs.... to cope with 500kg of fish...

Thanks for all the replies everyone.

All about the ratios...so how much gravel bed (only) filtration is necessary to handle 1000 tilapia @ say 500g each?

I would also like to know how much filtration (if any) a DWC element can provide to a system, especially if in this system there are gravel beds ahead of it?

I would laso like to know how much the introduction of a swirl filter would affect the overall filtration requirements of a system...

Getting detailed here I know...

I suggest you visit a Tilapia RAS system.... stocking 100-200kg+....

I bet you wont see a gravel filter within a 1000km...

500kg of fish is a serious RAS operation.... and should be treated, and approached... as a serious aquaculutre system....

Personally... I think you would be pushing it... even with Tilapia... to stock 500 fish in that sized tank....

And given it's an above ground pool... which have been known to fail.... personally... I wouldn't be putting more than 100 fish in there... and that's about the limit of your ten bath tubs anyway...