Backyard Aquaponics
A place to discuss aquaponics

Hey Everyone

I have a few newbie question if you could possibly help

I am in the process of planning a 1500 litre fish pond system

What size growbed should I look at getting?

Will it be a problem with the water level continuously rising and falling?

If I use the Bell Siphon method won't there always be a some water left in the bottom of the growbed?

As the growbeds act as the bio-filters and nitrification processes... the capacity of your growbeds will determine the amount of fish you can carry..

In general we recommend that you have at least as much growbed capacity as fish tank capacity... i.e. a ratio of 1:1.... with a stocking density of 3kg of fish / 100L

Any water remaining in a growbed after a siphon drain... would be negligible.. and of no concern, as the next flood would mix any remaining water...

So what determines the amount of water left over.....I presume it is determined by the size of the intake hole that is cut at the bottom of the outer pipe correct?

On the BYA site you can buy a drainage kit....however to me it looks like it will drain to the level that your standpipe is at and no lower....is this correct?

Not sure what you mean.... the bell siphon will break when the water level drops to the outlet pipe opening... allowing air to enter....

Where upon, the bed begins refilling... as a bell siphon arrangement utilises a continous pump


The overflow standpipe system employed in BYAP kits utilises a timer... which results in the pump being stopped.... as the water drops below the standpipe top (stops overflowing)... it continues to drain via one or two small holes drilled through the base of the standpipe...

Here's a standard BYAP overflow standpipe...

Most siphons do leave a couple inches of water in the grow beds. Generally water can only flow through gravel so fast and the siphon will manage to suck air before the bed is completely drained and in a continual pumping system, the bed in immediately re-filling as soon as the siphon shuts off so the bottom couple inches of the grow bed are never really drained. This in not necessarily a problem unless the grow bed is too shallow.

The BYAP drain kits are appropriate for Timer operation of the pump as Rupe noted and the picture probably explained your other question.

And as Rupe said, equal grow bed to fish tank is a good recommendation. The water level in the fish pond will fluctuate so the design should be through out to make that not be an issue. So long as the grow beds are equal to the fish pond, it will only take 40-50% of the water to flood the grow beds. If there are multiple grow beds using siphons and the pump runs continuous, then the water fluctuation will likely be less than that most of the time because the grow beds flooding and draining will usually not be in sync. Another option to reduce the fluctuation might be to use a pump on a timer and one of the Indexing valves Rupe has available (are they listed on your site yet Rupe?) check the link in his signature. The indexing valve (spider valve etc) are great in my opinion and then you could use the simple BYAP type stand pipes in the grow beds and the beds drain more fully and then you would even be able to run lots more grow beds than the 1:1 ratio and you might not even need to worry so much about level fluctuation or sump tanks.