Evaporation and Predation

[Greg Hershner]

Questions for those with outdoor systems.  I find I am adding water at least twice weekly.  Is this normal?  Can this be avoided with a greenhouse?

My smallmouth bass came up missing!  No trace/evidence.  Anyone have ideas to keep the critters away?  

[Nate Storey]

Hmm. It's not an issue of how often you're adding water, it's an issue of how much. if you're adding more than 3% daily, you've probably got a leak or way way to much surface area/volume.

As for critters, depending on what they are bird netting and lead tend to do the trick. but then again I live in Wyoming where giving pests high-velocity lead poisoning is a time-honored tradition. . . probably not an option for most folks though. If it's raccoons (a possilbe culprit, a dog, or a live-trap is an option- with racoons bird netting won't help. If it's herons, bird netting or changing the angle of your pond (I'm assuming this is a pond outside?) bank can help- make it too deep for 'em by eliminating the shallow portions of your pond. If it's neighborhood animals, a bb gun stings enough to prevent them from coming back, but won't do any actual damage (use round pellets at low velocities), or you could build a nice fence. . . They also make motion activated sprinklers- they work great for deer, but I don't know how they'd work with smaller animals like raccoons.

[TCLynx]

I'm finding that this spring the heat and now my lack of shade structure over my system is causing me to top up more than I used to. It is really hot here lately.

Keep in mind, plants can transpire a huge amount of water when it's hot, if you have lots of plants in and it is really hot/sunny/dry there, there might not be anything wrong, it could just be the plants using up the water. It all kinda depends how much water we are talking about.

Some things to check to make sure your design isn't loosing water for you. Splashing may assist in aeration but if the splashing is actually getting water splashed out of the system, it isn't good, that is just a waste of water.
And back to that splashing and aeration point, Aquaponics is all about balance remember. The more surface area that gets exposed to air, the better the aeration, however, the more surface area exposed to air, the more evaporation. What will be best will also require a balance of many things. In a dry climate you may be able to reduce evaporation losses with a greenhouse since in a more humid environment the plants won't transpire as much and humid air can't take on as much moisture so it can slow evaporation. However, if you get your greenhouse too humid inside you can run into condensation problems and fungus problems. Ventilation is important and air flow is important. And in a cold climate in winter, too much moisture condensing on the inside of the greenhouse and freezing can block light and even make it hard to open the door.

Here in my usually hot humid climate, greenhouses need to be able to open or roll up the sides and put up shade cloth to keep from cooking the plants in summer, otherwise they require cooling.

I keep covers with netting over all my fish tanks to deal with predators and also keep leaves out of the fish tank, it also helps to bounce the fish back into the tank if I have jumpers. Might not be as easy with a pond I know.

[TCLynx]

I'm finding that this spring the heat and now my lack of shade structure over my system is causing me to top up more than I used to. It is really hot here lately.

Keep in mind, plants can transpire a huge amount of water when it's hot, if you have lots of plants in and it is really hot/sunny/dry there, there might not be anything wrong, it could just be the plants using up the water. It all kinda depends how much water we are talking about.

Some things to check to make sure your design isn't loosing water for you. Splashing may assist in aeration but if the splashing is actually getting water splashed out of the system, it isn't good, that is just a waste of water.
And back to that splashing and aeration point, Aquaponics is all about balance remember. The more surface area that gets exposed to air, the better the aeration, however, the more surface area exposed to air, the more evaporation. What will be best will also require a balance of many things. In a dry climate you may be able to reduce evaporation losses with a greenhouse since in a more humid environment the plants won't transpire as much and humid air can't take on as much moisture so it can slow evaporation. However, if you get your greenhouse too humid inside you can run into condensation problems and fungus problems. Ventilation is important and air flow is important. And in a cold climate in winter, too much moisture condensing on the inside of the greenhouse and freezing can block light and even make it hard to open the door.

Here in my usually hot humid climate, greenhouses need to be able to open or roll up the sides and put up shade cloth to keep from cooking the plants in summer, otherwise they require cooling.

I keep covers with netting over all my fish tanks to deal with predators and also keep leaves out of the fish tank, it also helps to bounce the fish back into the tank if I have jumpers. Might not be as easy with a pond I know.