Backyard Aquaponics
A place to discuss aquaponics

Hi all,

I am new to aquaponics but not hydroponics. I have started a system that consists of a 75 gallon rubbermaid stock tank and 5 window boxes (36" x 5" x 5"). I am growing Kale and working getting my spinach started. I am using shubunkin gold fish (4 currently) and not sure how many fish I need to have to properly feed my plants?

Thanks for any input

Reed

The normal suggested ratio is 25kg of harvest size per 500 litres of filtration. That is what is suggested for Trout, Perch, Barra etc.

I've had a system running very successfully with Shubunkins for over 3.5 years now, and I've found that 5Ltr of WET gravel per fish gives excellent plant growth without any Ammonia issues. Don't include the dry top layer of gravel in your calc's... and you should have a dry top layer. The max water level in mine is about 40mm below the surface of the gravel.

The gravel in your GB's isn't very deep, this is limiting the amount of fish you can stock in ratio to the square meterage of GB/plants. The way it is currently set up I don't think you will have sufficient nutrients per sqm for good plant growth.

I would fill the GB's almost to the brim with the expanded clay gravel and raise the max water level, therefore giving you more wet gravel... which equals more bio-filtration... which equals more fish per sqm of GB... which equals more nutrients per sqm of GB... which equals healthy plants.

Golfish, being essentially carp, are a pretty dirty fish, so you won't need as many as you might for other fish.
Having said that, goldfish also don't need the same amounts of dissolved oxygen as trout etc, and won't grow as fast as them either, so you can keep more if you would like to.
How big are your goldies?

Looking at those window boxes I can see they aren't full to the top, so keep that in mind when working out your filtration.
You need to work out the amount of 'wet media' you have, so work out how high the water goes to in your set up and use that in working it out.

Without doing the maths, I would think 4 might be a little on the light side for nutrients. But always better to add more if you aren't getting the plant growth you want, than to try and find new homes for them if you're overstocked from the beginning. At a rough guess I would say at least 10 goldfish would live quite happily in that set up. But I will leave you to do the maths re your wet media, as I can't quite tell from the photos.

Oh, and welcome to the forum!! It's great here

Man, that means I need 450 odd goldfish in my system.

I was working on 10L wet media per fish.

Oh, Mr Damage beat me to it He is much more knowledgeable than me so you're in safe hands.

I guesstimated around 70-80L of wet media in your set up, so my suggestion was a bit more conservative, but I'm still a newbie, so my suggestions will stay conservative for now hehe.
Thanks Mr D!

Thanks for all the input. I don't let the water have any depth. I have been growing in a running water system also know as nutrient flow technique using leca (hydroton) for many years. I have never done it as an aquaponic system so changing from fertilizing to fish is new for me.

I did the math and looked at how much clay was left in the bag I opened and figured I have used about 50 liters of leca so far. The clay is moist through out and dry on the surface. also as my plants mature I will add more leca to the top for support of the plant.

I went to my local fish store today and had them check my water and ammonia was good. I think I will add two more fish for now as the system is only two weeks old. Oh and the fish are about 5" long.

Thanks for all the input. I look forward to learning and welcome any advice.