dilution from rain?

[Kristen Langhorn]

I`m also starting up a basic barrel system.  I have many of the same start up questions as Greg as far as shelter and shade.  Do we have to be concerned about the rain diluting the system? Currently I`m watching wet snow falling outside.  Which brings me to my next big question.  What sort of fish will survive in my area?(Sherbrooke Québec, Canada)  I know where I can get live Catfish, Tilapia and Troute.  The Catfish and Tilapia are both from Chinese grocery stores, should I be concerned with the health of the fish?

This weekend I`m hoping to sort out the plumbing of the system.  Our stand is already built.  So exciting!

[TCLynx]

Tilapia are sub-tropical fish, they need rather warm water to grow and at least 55 degree F water to simply survive. If you are not going to have at least 6 months of water over 70 Degrees F, then you probably don't want to grow tilapia. In your location, I expect you would need an indoor or heated system to make tilapia feasible.

Catfish are thought of as warm water fish but they can survive freezing water. I would recommend getting catfish that you know have been raised in your climate if you want them for an outdoor system since you want something that will be bread to at least survive in your climate.

Trout might be a better choice for your climate, they are a cool water fish. In summer you need to increase filtration and aeration for them if the water starts getting too warm or make some adjustments to help cool the water a little but that should be reasonable in your location.

I've never grown trout but I have a fair bit of experience with Channel Catfish and Blue tilapia in central Florida. I was not willing to heat my water to get better growth out of the tilapia and we like catfish better anyway so we are sticking with channel catfish as our primary fish now.

[TCLynx]

As to the question of dilution from rain. Well, this might be a somewhat complex answer. If a system is high on nutrients but low on plants, then a bit of dilution might be a good thing. A system that is heavy on the plants but with minimal fish, dilution might leave the plants competing for a limited substance.

If you are planning a relatively small system and the grow bed volume will only be equal to the fish tank volume, and you are planning on edible fish, then I expect you will have enough nutrients to handle a bit of extra dilution on occasion. Of course a few weeks of heavy downpours might make me a liar. My system in outdoors in central Florida and even with heavy rains, I've never had a nitrate reading get low enough for me to worry about dilution robbing my plants of nutrients. I need more plants to keep up with my fish.