Growing LOTS Of fish

High Density (HD) Versus Low Density (LD) Systems

Low Density Systems (LD) We developed our LD systems after receiving many requests for an economical, viable, off-grid aquaponics system. The goal of this system was to only use one-fifth of the electricity and fish food that our original UVI-style systems did, but have the same vegetable production. Our first LD system was our Family System.

(Below) We’d always wanted to raise lots of fish; what a disappointment we were in for!

Our original systems designed after the University of the Virgin Islands (UVI) model had solids settling tanks (UVI calls these clarifiers), fine solids capture tanks (UVI calls these net tanks), and degas tanks, and we ran them with 1-1/2 to 2 pounds of fish in the system per square foot of raft area. Because of this high density of fish, we now call them HD systems.

The design criterion of the UVI systems was based on growing as many pounds of fish as possible, while not being overly concerned with the cost of raising those fish. It’s understandable how this can occur in a university environment where the university pays the bills, and the program never has to stand on its own feet financially.

What we discovered, after our first year of operation (2007-08) in a commercial environment where we had to pay all our own bills, is that the fish portion of the operation loses money. Our fish cost between $4.00-4.50 per pound to raise up to market size, and we sell them for between $2.00 to $2.50 per pound wholesale, because we compete with cheap Chinese imports. This realization came at about the same time we developed our LD systems, whose original design goal was simply to make a lot of vegetables and not require a large and expensive off-grid alternate energy system to power them. These LD systems also satisfied the goal of growing as much vegetables as possible while losing as little money as possible on the fish portion of the operation.

Our LD systems run on about one-fifth the fish the UVI systems use (around 0.3 pounds per square foot of raft area), but have no clarifiers, net tanks, degas tanks, nor sump tanks. Needless to say, they are a lot less expensive to operate, using only one-fifth the fish food and electricity to aerate the fish, and they are also much less expensive to build! These LD systems are organically certified (and certifiable) both by Organic Certifiers of California, and Oregon Tilth of Oregon.

High Density Systems (HD) – These systems have solids settling tanks, net tanks, and degas tanks; these tanks are all necessary in order to get rid of the excess fish poop that 1-1/2 to 2 pounds of fish per square foot or raft area will generate. This is the way aquaponics was taught to us by UVI: their system was developed by aquaculturists trying to grow as many fish as possible while keeping the water quality high at the same time. It seemed like such an “of course”, that nobody questioned it: of course you would want to grow as many fish as possible. We didn’t question it either until we lost $2 per pound on the 6,000 pounds of fish we raised and cost-tracked that first year. Maybe $12,000 is not much to you, but Ouch!

This is in stark contrast to the more common philosophy many aquaponicists support of trying to grow as many fish as possible. We think they do this because:

1. Regardless of size, they are really only “backyard” operations that don’t analyze their financial data.
2. They’re still operating on someone else’s investment capital rather than income.
3. Someone else pays their bills for labor, electricity, fish food, and the cost to build and maintain their facilities; like a university, some investors, or a trust fund.
4. They’re really making their money from selling system kits and trainings, and have never had to be profitable growing vegetables.

THERE’S ONE GOOD REASON TO BUILD AND USE AN HD SYSTEM: Please don’t think we are dismissing these systems, because we’re not. There is a single good reason to build and use an HD system, and that’s if a number of economic factors line up exactly right for you in your location: If you get good prices for your fish, and have cheap electricity, and have very cheap fish food and labor, (and have run the numbers on all this to make sure), then the most productive and profitable system is an HD system just like our original UVI-type systems, which will grow more fish in that economical climate. They have more tanks, more plumbing, and larger blowers, but they may pay for their increased cost very quickly with the increased fish production.

But if you didn’t run your numbers carefully, or didn’t run them at all because you were seduced by the siren call of: “grow lots of fish”, then please don’t complain to us when you lose your shirt trying to grow lots of fish, whether it’s in an aquaponic system or an aquaculture system. Bottom line:

If you add your costs for raising fish (fish food, electricity, and labor) and find that they are MORE than the wholesale price you get for your fish, the most productive and profitable aquaponic system is an LD system (because you are losing money on the fish!). These LD systems are now organically certified (and certifiable) by Organic Certifiers of California.

If you add your costs for raising fish (fish food, electricity, and labor) and find that they are significantly LESS than the wholesale price you get for your fish, the most productive and profitable aquaponic system is an HD system (because you are making money on the fish!). These HD systems are organically certified (and certifiable) by both Organic Certifiers of California AND Oregon Tilth of Oregon.

You’ll find lots more info on organic certification in the Blog Category of that same name!