Backyard Aquaponics
A place to discuss aquaponics

Hi,

I'm a newby and still struggling to conceptualize an outdoor system. I'd really like to design a small system with one length of 4-6 inch diameter pvc pipe. However, taking into consideration the 1:2 rule, my fish tank would be tiny. I'd also like to have it as an outdoor system. What are the basic guidlines if I'd want to try a ratio to a 1:1? And what are the basic guidelines for an outdoor system in general? I live in Southern California - averages about 11 days of rainfall per year. Winter weather is from end of November til March. Temperatures seldom drop below 40F. Pretty much sunny the rest of the year. Highest temperatures during heatwaves just above 100F.

Any advice would be greatly appreciated.

Thanks,
W

Hi Wartooth and welcome to backyard AP
My system is an outdoor system, I live in a temperate climate our average rainfall is about 28" per year, rains about 150 days per year. We get a few days of frost, average low in winter goes down to 38F, this summer we have had 5-6 days over 110F but the summer average is about 85F.

If you do a search you will find lots of discussion about the 1:2 rule. In my observation most systems are actually more like 1:1, to truly get to 1:2 or more you need to have a system to fill growbeds in sequence. This is what I have done with mine, but at the moment I am still running about 1:1 ratio. I have a CHIFT PIST system the tank is about 1100L and the sump is about 600L so in total I have 1700L I currently have 2 GB's at about 800L each they remove about 400L from the sump each time they fill, I can sequence up to 4 GB's. Do you really only get 11 days of rain a year? Whats your annual rainfall? Having the system outside means rain can enter the system so have it designed with an overflow to carry excess away, unless you have very heavy down pours I would not be too concerned about diluting the nutrients as they are replaced continuously. You also need to cover the tanks both to stop light levels causing alge growth and to prevent leaf and litter falling into the tank. I recommend 90% shade cloth.
If you are going to have a tiny tank you will have problems with temperature variation that can harm the fish, a large volume of water is better than a small one and you could insulate the tank. Why are you considering a tiny tank? Is it because you want limited GB space? With AP the tank can be much larger than the available GB the real key is the ratio of fish to GB, for instance in my system I could carry about 30Kg of fish if I doubled the size of the fish tank and did not change the GB's I could still carry 30Kg of fish but not 60Kg. The nutrients are continuously provided and the plants can still access them in in the greater volume of water.

Thanks Novaris! Your fish tank size advice eases my mind a lot. I was reeling with calculations non-stop. So now I can just concentrate on number of fish rather than tank:bed size ratio.

Yes and no Wartooth... the ratio of growbed volume to fish tank size is important because it provides for the filtration requirements for the number of fish stocked... at a level of 3kg/100L

That level of stocking is advised as it is a safe and maintainable level with a filtration capacity of, as a minimum, a ratio of 1:1....

A mature system with either advanced growth fish, or stocked at a higher density requires a greater filtration capacity... approaching 2:1...

This is because, (with bigger fish, or more of them), you are feeding more and the fish are creating more waste (uneaten feed and fish excrements, particularly ammonia)... hence the need for increased filtration capacity....

So as your fish grow, you may need to increase your filtration capacity accordingly... by adding more growbeds....

So yes... number of fish to tank volume is a critical factor that people can often overlook... they see a lot of small fish in what seems like a lot of water... and forget that with growth... there's a lot more fish mass... for the same amount of water...

But that the larger fish are exponentially increasing the waste nutrient load on the volume of water.....

In a nutshell.... try to aim for at least the same volume of filtration capacity (growbeds) as your tank volume... size your pump/pump cycles such that you turn over your tank volume at least once an hour....

And stock your fish to the level of your growbed filtration capacity.... not your tank volume as such... as this is the limiting factor....