Backyard Aquaponics
A place to discuss aquaponics

Just getting started in AP, and all I have is an old bathtub that currently has lillies growing in it. I just want to start with something small, and don't know whether I should use the bath for a grow bed or fish tank. Perhaps a grow bed would be a better use for it?

If I use it as a grow bed, what size fish tank should I aim for?

If I use is as a fish tank, what size grown bed?

At this stage, edible fish production is a want not a need. If I use it as a grow bed, a mate can weld me a stand for it, and I'll probably use gravity to drain into the fish tank.

Suggestions/advice most appreciated.

Ranga

G'day Ranga,
a bathtub can be used for either but my preference would be to use it as a GB

Fish Tank
ideal water depth is 600-800mm...too shallow and the water temp ranges too much, go deeper and it becomes a chore to harvest the fish

Volume - the greater the water volume, the more stable the system in terms of daily temp variations and nutrient levels, Bunnings are selling 500 litre water tanks for $59 or you may have something else in mind - my preference is to have a round fish tank but some are using the 1,000 litre IBC very successfully.

The general rule of thumb is 2:1...200 litres of GB media to 100 liter of fish water will support a maximum of 6kg of fish weight (this is the max levels for experienced Apers to have nice healthy fish and plant growth)

My system is 3,000 litres of fish water - 3,000 litres of GB media and 18kg of fish
or my FT/GB ratio is 1:1 which is capable of supporting ~90kg of fish - so I am in no way stressing my system

I recommend staying below 3kg/100l of fish water and the system will hummmmmmmm

Digest what others will be advising as well then toss up a few more questions on what you don't understand

Use it as a growbed, and use a 1/2 IBC (if you can get them cheap) or use the bunning ones as the fish tank.

Pump in IBC, drains back from bathtub.

So, if I were to get a 500l tank from Bunnings for the fish, how many bathtubs GBs and how many fish (probably silver or jade perch) could this support?

Also, given that could bury the FT a bit to ensure the GBs could gravity feed back to it, what pump would you recommend? Also, being the simple setup that I'm planning, would you recommend a float or electronic timer for the pump?

For 500 liters - aim for 10-20 nice sized fish = 5-10kg - which will require 2 bathtubs to run without getting into trouble. This gives some room for larger or more fish once you are experienced.

Use a 1000lph cheapy pump from ebay or somesuch, 1/2 hour on 1/2 hour off to get started via a standard $8 bunning timer. As you gain experience in running the system, modify the timing to suit your application.

I wouldnt worry about standpipes etc in a bathtub, just run the water inlet line down the middle of the bathub, with 6mm holes about 5cm apart, and drain out the bathplug hole.

Thanks for the help. I'll keep my eye out for another bath tub and pump.

http://cgi.ebay.com.au/Submersible-Fountain-Pond-Water-Pump-1500L-H-NEW-Jebao_W0QQitemZ260279909467QQihZ016QQcategoryZ20754QQssPageNameZWDVWQQrdZ1QQcmdZViewItem

The one above will give you around 1000lph at your bathtub height.

Inneficient, not quiet (but you know they are working), cheap.

I had 6 of them all up - only 1 has died so far - and they have been run dry quite a few times.

One remains in service with 4 as spares

Love that built in redundancy OBO

Log all the queries and what you are not sure on and we can cover it on the w'end