Notes from Windward: #66


The Mini-Aquaponics System

developing our middle-sized test platform

  November 16:

     Now that Vermadise is pretty much sealed up for the winter, we'll be spending time getting the mini-aquaponics system prepped for next spring. One of the first things that needs to happen is for the concrete to finish curing since the chemical processes involved will affect the pH of the water contained in the concrete tank, something which would make it difficult to keep the pH stable for the fish. Indeed, mastering the control of system pH is one of the key skills we'll want to perfect using this middle size system, and the last thing we want is for the chemistry of the concrete to interfere.

     We're very pleased with the quality of drinking water we have at Windward and the way that our gravity-operated water delivery system is a good example of passive design in action. Our main potable water system is rigged to fill and overflow our primary 3,000 gallon storage tank so that water delivered to the kitchen is always be fresh.

     The system works very smoothly and it's easy to forget about it until something happens to draw our attention such as an incident this summer when a brass water faucet, evidently weakend by freezing, just burst open during the night. That was a rare sort of event, and otherwise about the only time we run out of drinking water is when someone goes to fill up one of water barrels, say for the sheep, and leaves the hose running. I can't tell you the number of times over the years that this has happened, and way too often I've been the guilty party, so the rule is that when filling a water barrel, stay there until it's full--bring a book if necessary--and then make sure that the hose is turned off before going on to do something else.

     We divert the overflow from the tank to a variety of non-potable uses. For example, in summer, the water flows into three six-hundred gallon tanks that supply the summer shower. One reason for that set up is that if anyone leaves a shower running, it will only drain one of those six-hundred gallon tanks instead of the whole system. At that point it's easy enough to shut off the offending faucet, open the valve on another of the six-hundred gallon tanks and the show is back in operation.

     Well, the summer-shower's water heater has been dismantled for the winter [to protect it from being damaged by freezing] and there's no longer a need to capture overflow for use in the gardens, so we connected up about four hundred feet of garden hoses to route the overflow water down into the 1,250 gallon concrete tank that will form the heart of the mini-aquaponics system.

using over-flow from the water tank
to fill the mini-aquaponics tank

     The primary difference between the mini-system and the full scale system is that the water in the mini-system won't be heated. There are enough variables to deal with in getting the water flowing to the right places at the right times--consistently--without also having to focus on keeping it warm enough for the tilapia to prosper [they like water that's 75° or warmer] so we'll be using initially be using cold water fish such as trout and carp in the mini-system, and plants that do well in cold weather such as kale and kohlrobi.

     When we start working with tilapia, we'll have to have our breeding stock flow in, and so it's better to work out the kinks in the system using inexpensive, locally available fish. That way when we make mistakes--and that's something you can count on when bringing a new system online--the "lessons" won't be too expensive.

     When the tank fills up, we'll set a siphon to drain it out, clean out the leaves and acorns from the bottom, and then allow the overflow to fill it up again. We'll repeat that process until the pH tests stable.

  November 22:

     No break in the rain, but at least the temps are staying around 40°F. We'd like to do more work on the ourside of Vermadise, but there's not much point in trying to do anything that involves excavation since it's too muddy for that sort of work by now. No problem though since there's always a host of things that need attending to indoors, and this is the time of year when the kitchen is both warm and fragrent as there's usually a pot of soup simmering on the woodstove, or something baking in the oven.

     Now that the run-off from the main water tank has filled up the 1,250 gallon fish tank, the next step is to drain it so that it can fill again. Otherwise, what will happen is that water will flow in at the top on one side, and then exit through the outlet at the otherside, without actually flushing out the tank. Our goal here is to leach the concrete so that when we put fish into the tank, the chemistry of the concrete won't throw off the water's pH and harm the fish.

using a hose to drain the tank from the bottom

And so the best way to do that is to use a hose to siphon off water from the bottom of the tank. Once the siphon has done it's work, the suction will break and the tank will start to refill. We'll repeat that a few times until the weather gets cold enough to freeze the water in the hose, and then leave retreat into Vermadise until we're on the other side of winter.

Notes From Windward - Index - Vol. 66