As someone who has actually and still actually runs both types of systems, I feel I can comment here. I run a flood and drain system, chift pist, 6000 litre sump, 5000 litre tank, 4 x 2000 litre growbeds. The system is currently holding around 120 kg's of fish. I feed around .8 - 1.2kg's of feed a day. Last summer I had a huge rat problem that strung out into winter so I didn't plant any winter veg in that main system. I have concentrated on rat proofing and eradicating them. That having been done, self seeded tomatoes from last year are flowering and the system is kicking on nicely. The lesson here is, that because I have absolutely shit loads of BIOFILTRATION, I can run a fair few fish in there. I designed the system to cope with 50 kg's of fish per 1000 litres according to the 2:1 ratio thingy. So far, so good. I am half way to that mark and I haven't lost a single fish touch wood, in 6 months. The system requires virtually zero maintenance. The growbeds are literally teeming with worms, the water is clear etc. All I do is top up the sump as required and feed the fish. And when the fish go a bit slow on the feed, they need a bit of fresh water, because of NITRATES not AMMONIA. Hence the BIOFILTRATION. You can have plants coming out of your ass, but if you don't have the filtration to handle to fish load you will kill them.
Conversely, my small test sized commercial lettuce growing system is being wound down. In order to get maximum growth out of the silvers, they need to be held at above 7.5 ph, and lettuces etc require ph in the 6's for fastest growth. The system is complicated, expensive to run and time consuming to operate. All related to solids removal and the power required to force water thru a pressurised bead filter. Pre-solids filtration is expensive to do properly, and time consuming, and involves expensive components to do it right..
In my gravel bed system I have NFT add-on with screen filters on the feeder lines . This is relatively simple. The substantial growbeds trap a fair bit of the solids, the screen traps a bit more, but the chanels eventually need a good clean out. Any holes that don't have a plant in the promote algal grwoth.
Having been doing AP now for 3and a half years, I can only come to one conclusin. Trying to do it commercially to grow fish and plants for profit? Don't bother IMHO. The scale that you need to produce it all on requires dollars with many zeros after them to even get started. I sell my veg at the local school every couple of weeks, whatever I have that we don't eat, mainly lettuces, and it pays for the pumping costs, but no profit as such. The real pleasure is eating the snowpeas straight out of the growbeds before the kids get them, or taking a handful of broad beans in to heather cause I hate em but they did well in a system un disturbed by rats
The only people making any money, out of systems the size of the one in Mildura or others similar like ours, I would guess, would be the people who charge a fortune for the set up and commissioning of the systems. Fish growth rates quoted by consultants rarely take into account temperatures, I even heard of someone telling his client that the silver perch he had supplied him with would be plate size in 8 months, just bullshit. Unheated past 17 degrees, mine would be 2.5 years to plate size. Minimum. At 27 degrees, 1.5 is my guess, but the cost of heating them would take any profit out of them at all.
I get a bit sick of people banging on about commercial systems, because to me, unless you have made a profit, employed someone to pick the stuff and feed the fish and managed to spend a few days a week sipping pina coladas by the pool, it ain't commercial, it is just supporting the consultants very large and warped ego. This post sounds a bit jaded I know, but I am just telling it like it has been for us. AP is the worlds most valuable hobby, I can't imagine my backyard without a system or 4. But people who feel the need to bang on about what they are going to do and how good it is going to be, just to support their flaming huge egos and to compete with people they have fallen out with who are at the forefront of this industry is just pathetic. I too would love to see both pictures and updates of how the system is looking and performing both $ and produce wise in 12 - 18 months, but I wouldn't mind betting it all goes very quiet.
Backyard Aquaponics
