Firstly, and most important is for the electrical feed in your setup. This must be protected with a GFI plug. You are dealing with water, many electrical appliances, and mains level electricity. Either your feed should be from a GFI protected plug (shown), breaker, or extension. The GFI will trip the electrical circuit should a current be detected on the ground line (the start of a fault).
Secondly, should have an overall water circulation failure plan. You can have the following failures, and I have listed my safety mechanisms:
1. grow bed drain failure (clogging) // overflow mechanism
2. sludge separator outflow failure (clogging) // overflow mechanism
3. water loss (either 1,2 above or pipe failure) // minimum water level in fish grow tanks
4. water in greenhouse // drain capability
My safety mechanisms are implemented as follows.
The overflow mechanism on the grow beds are either a drain to an adjacent grow bed, and/or an overflow directly back into the grow bed.
bed to bed overflow allowance
over flow pipe on my sludge separator (the unconnected pipe on the left -- it is normally connected with a hose directly back to the fish tanks
green overflow pipe directly to fish tankThe minimum water level in the fish tanks are provided by having the pump not be able to pump the tank dry. My pumps are set to draw air at about a 6 inches (15cm) of water. You do this by raising the pump at the bottom of the tank or situating it so it's input will hit air at your desired depth. This is important so that if you do get a pipe failure, your pump will not eventually empty your tank and kill your fish.
When you build your greenhouse or aquaponics enclosure, keep in mind you are dealing with water. There will be times you want to empty your tank, have accidental spills, have accidental overfills, and other reasons why you will have water on the floor. Don't worry. And don't make your walls waterproof sealed at the seam to the floor -- this will allow the water to escape. If you did caulk or otherwise seal your wall seams, open a few water channels around the perimeter.
Third you need to have protection for overfeeding. I have had the most trouble with inconsistent feeding. This could be for a number of reasons and I have not determined the root cause. The solution for this is to feed minimal amounts with your auto feeder. I then manually top the feeding so that I can control it. What does this mean? If I am travelling, I set my auto feeder to only feed once a day (in the afternoon). I then feed the fish myself up to two more times during the day (morning and evening). The fish survive fine with the single feeding.
Fourth, you need to have precautions on your air hoses. This is to prevent water back pressure from returning along the air feeder lines and flooding your air pumps. The precautions taken here are two. First, and ideally you place the air pumps above the water level in your fish tanks. Sometimes this is not possible. If not, then the two methods applicable are to use one way air valves on the lines (of limited usefulness but part of the strategy), and a looping of the line (here you can also take the line first above the water level, but due to vacuum affects this alone will not prevent back feed). Even using these precautions note that a power failure in my home one day caused water backup into one air pump that caused a leak and, fortunately, triggered my GFI extension -- otherwise I would have stepped into a puddle of live power when trying to find out where the water was coming from.
In the future I want to connect the feeder, pump and a camera of my setup to the internet. This will allow me full control while travelling.
