Backyard Aquaponics
A place to discuss aquaponics

I have been thinking about my next system (larger of course) and what problems I wan't to not avoid in the future.

My current problem/grievance with the current sytem:
I have 8 half barrels, similar to Joels barrel system, all of which are filled at the same time from the 1 pump. Now to get these to fill at a rate that was even remotely similar to each other I had to put valves on each of the water inlets for the beds and then make sure that the timer on the pump goes for long enough to fill the slowest one. Water doesn't seem to distribute itself evenly through multiple T junctions... In addition I had to make sure that the overflow for each bed had to allow more water out than what could be pumped in, thus not having any overflowing GB's.

All of this took time, changes to design, fish losses etc that don't need to be repeated on the second attempt. All is working well at the moment and everything is in balance, so I don't want to change anything on the current system.

So my thoughts are:
1. Only have 1 grow bed but make it a big sucker. I was thinking in the order of 10m long by 1.5m wide with access down both sides. This way there is only 1 LARGE drain and one bed to fill. This would completely avoid any of the above problems mentioned. However making a bed this size would be quite difficult and would not really be able to be moved once built. It would also require large amounts of support as it would hold over 4,500L of gravel/expanded clay balls. (shudder at the thought of gravel washing) I do have some good ideas on how such a bed could be made quite cheaply with roofing iron and sealant - so that isn't such a problem.
Alternativley
2. I could continue to have multiple (but larger) grow beds all plumbed as if they were one. What I mean is they could have pipes connecting each other horizontally, so that if one fills up faster than the other is would level itself out with the others possibly? I am thinking something like the size of Joels lovely GB's all lined up one after the other.

They could all have seperate water in pipes and possibly all have water out pipes or perhaps could have just one water out pipe from one of the beds?

Could this work? Do I need to draw a picture?

Fizzy a balance pipe/tube/conduit.
The only issue I see, is that should the balance pipe be dislodged,
obviously all the water will be lost, and the pump would continue.
( which happened to a friends rainwater tanks 2 X 20k Gal.)
I would think the passive nature would ensure the water levels evenout.
though you would end up with a large dump of water and a reduced minimum level if all are in sync.

Other options:
1- Several medium GBs with multiple pumps, That way you only have to balance 2-4 GBs, and can have the "pods" of GBs staggered to keep from having all your fish in little water.
2- As you said with multiple GBs, but take slotted corrugated pipe, cut it in half, and run it down each side of your GB. Balance your drains on one side, balance your inputs on the other side. That way, the beds act as a single bed, but would tend to have flow running across the beds from the input pipes (all ganged together) to the drain pipes (all ganged together).

I would tend towards option 1 above, since that way you have some modularity in the event of trouble. You would also keep your fish in more water.

another thing to consider,
when you have large/huge grow beds it takes a long time to drain them. The big grow bed 3500L and the medium bed 2000L drain into 63mm pipe, back to the sump. It takes more than an hour for them to drain.

Making one big growbed or connecting several smaller ones together doesn't seem very different to me (as long as the pipes connecting the growbeds are big enough).

I take it this is going to be flood and drain? Will you use an autosyphon? Because if you are, then it could be difficult; EllKayBee's findings mean that any growbed with an area over 3 square meters won't work, because the minimum inflow for the autoshypon to kick in is always above the maximum water out of the inner tube.. This problem can be overcome by using a good U bend water slot at the outlet, but it might not be enough for such a big GB.

To drain such a 4500L GB in about 10 minutes, you'd probably need a 75mm INNER tube (giving you about 21.000L/h theoretical max out) and a 120mm outer tube, and for a nice 2:1 ratio you'd need about 7000L/h pumped into the GB!

Bloody hell, I'd love to see such a monster autosyphon kick in!
*drools

I tend to agree with Jaymie, as you get bigger , you're going to run into issues with draining as it takes time for the water to flow through the gravel.. You could try a distibution box like I have on the barrel system, it's been working well for a long time now, distributing the water evenly to 8 different barrels at the same time...

I don;t think a siphon would work to drain a bed that big as the water won;t be able to drain through the gravel to the siphon quick enough..

You have some good suggestions already, but to get good equal pressure and flows of air to multiple outlets (eg air stones) You use a closed loop of pipe connecting to the air pump, and then run everything off this loop. I know water is very different in basically every way, but it might work the same as air.....

I can tell that my experience of hooking my growbeds together for about levelling did not work well. For some reason the auto siphon would stop. It probably had do to with my levelling pipe being near the bottom. It mike work if the pipe was say halfway up.

Good suggestions guys.
Was not planning on autosyphon. It was going to be flood and drain.
It is good to hear some of the issues with going big.

I like the idea of the distribution box for my current system, that would have worked well.

Would it work as well on the systems you have recently put up joel? how do you manage the levels of each bed ? Will go and check the system thread to see if there is anything.

I don't like the thought of a leaky cross member losing all my water.

Fizzy, One large grow bed sounds good to me. You could have 2 or 3 drains but all going into the one pipe that heads down to a flout above the fish tank. One pump in the tank on continually might work or you could go for a sump and fish tank above the grow bed if you wanted the fish tank to have a constant water level.