grow beds

[Lee]

I would like to use a 6'' PVC pipe cut in half length ways as my grow bed, how long do you think i could make this using a 50 gal tank. We will be growing tomatos. New to this and really looking forward to it. How close should the water come to the top of the growing medium. thanks

[Murray]

Hi Lee,
The accepted wisdom on grow bed to fish tank volume is 1 to 1
So if you have a 50 gal tank then you can safely run 50 gal of grow trough volume. (whatever length that works out to be)
This needs to be balanced with enough fish to produce the required amount of nutrient for the plants intended to be grown.

Ideally, the water should flood up to just below the surface of the gravel or other grow medium at the top of the flood cycle. This height is not critical and plants will do well so long as most of their roots are flooded during the flood cycle and allowed to be exposed to the air during the drain cycle.

It is all about balance.

[Hamish]

Are you considering making a flood and drain style system? Or a hydroponic style NFT system where a small trickle of water is pumped through the pipe?

Have a look at post 76 in my thread http://www.aquaponicshq.com/forums/showpost.php?p=4579&postcount=76 I have posted some pictures of my grow beds and the return pipe.

The return pipe to the fish tank will have holes cut in the top to sit plastic basket pots of strawberry and lettuce plants. The plant roots dangle in the flow of water that runs through the pipe each time the growbeds empty.

If I find that the plants dont like the iregular flow of water then I will also add a small trickle from the pump to also run through the pipe back to the tank.

[Lee]

thanks guys, the plan was to have a constant flow of water, if i choose to flood and drain how often should this process happen.

[Hamish]

My system currently takes about 12 min to fill and empties in about 2 min.

[Hamish]

My system currently takes about 12 min to fill and empties in about 2 min.

Actually - after drilling a small 5mm hole at the base of each siphon standpipe the growbeds now take about 16min to fill and 1 to 2 min to empty. Longer to fill because there is always a small trickle of water running back to the tank.