A couple of problems have already arisen.
I filled one bed and trickled water in to test the speed at which it filled and although having copied diagrams for drainage pipes I soon realised that the beds were going to drain much quicker than the presumed water would fill them. So I closed up some of the holes I had drilled and I think it will still be too much and am entertaining the idea of even no holes and simply allowing the water to fill from the base of the pipe and rise with the rest of the water.
If need be I can always then add holes and in retrospect should have instead checked the operating of the drainage before drilling holes to see what happened.
The other thing that occurred was a couple of hours after filling the grow beds with the gravel the bolts holding the wooden beam that kept a corner of the benches up snapped in half under the weight and the bench tilted back against the house. Not very happy with that. I took my brother and Dad out to show them the progress and I thought my eyes were playing tricks on me!
I think I have a solution to the problem but will still probably have to empty some of the beds out to work with the bench a little easier.
Before I filled the beds I wanted to make sure that they were going to fit together well so took the time to cut some of the excess plastic rims off so that they could fit a little closer. I think this was a wise move.
I have ordered a water pump online due to its energy efficiency and its ability to pump the water much higher than required. I am expecting the lessened work load to mean an increase in speed and pressure given the short travel distance which would mean the grow beds fill quicker and more efficiently and drain slower allowing a good soaking of the gravel. I imagine I may have to cut into some of the stand-pipes so that they drain uniformly with the others.
The next challenge – once I’ve fixed the benches again! – will be to fix the piping will carry the filtered water back to the fish tank. Ideally I wish to make its journey quick and simple which will probably involve passing straight through the wooden boards to the tank. Quite a narrow space but the extra pressure built up may be good for aerating the water as it passes back into the tank.
I still need to do something with an overflow for the fish tank as any rainfall collecting in the grow beds will increase the water level of the tank. So as a back-up I will need an overflow, rather than just letting the water spill over the tank. I would rather direct this nutrient water to one of the garden beds.