Galvanized Tanks and Alkalinity

[reptilegrrl]

Some of y'all may remember me, I started out here with a 150 gallon rubbermaid tank for my pond. A few years ago, I added a 300 gallon galvanized stock tank to give my turtle some more space. For a few years the steel tank was fine. But in the last year I've had a lot of problems with it. Green water almost all the time (cleared up briefly when I added some aquarium plants and inadvertently brought in some brown diatom). Plants were puny or wouldn't stay alive.

The ph of the tank has been rising and rising. I live in an area with hard water. But, I still have my old rubbermaid tank in use, and the water in it is clear (in spite of having few plants and no biofilter) and the ph of that tank is always lower than the ph of the steel tank. I have added ph reducer to the water; sometimes the ph will drop briefly, but it always goes back up. Right now it's in the "8.4 or above" region on the test strip.

Is it possible that the zinc is dissolving into the water and raising the ph? Is zinc alkaline? Is this because the tank is 4 years old now? Oddly, I know people with older water gardens in galvanized tanks, and theirs are doing fine.

I'm considering just selling this tank and replacing it with a large plastic one, but if there is a way to mitigate this instead, I would love to know.

[dperry]

You have a turtle in the galvanized tank.  What kind of filtration are you using?  Algal growth is a result of having too much nutrient in the water, likely from the turtle.  Do you do water changes?  Decaying fecal material and other wastes produce ammonia, which raises pH.  What animals (fish or turtles) do you have in the Rubbermaid setup?  300 gallons is not a lot of water for a turtle unless there are significant water changes or effective filtration, both mechanical and biological, to remove the wastes produced by fish and turtles.  The galvanized tank is not causing your pH problems.

By the way, your signature lines indicate a "box turtle" in a wading pool.  You realize that a box turtle is not a water turtle.  They are terrestrial, though they like to soak occasionally.  They need a terrestrial environment with shallow water available.

[Pam]

I am pretty sure that RES stands for red-eared slider, definitely aquatic 

[dperry]

Pam

Look one line above the one to which you refer:

"2013: ~40 gallon in-ground wading pool for my box turtle"

I was wondering if she kept a BOX TURTLE in a wading pool full of water.  I know that a Red-eared slider is aquatic, but a box turtle is not.