Alkalinity Range?

[robocop]

What is an ideal range for Alkalinity in a Fish Only tank (dKH or ppm KH)? Does the range vary from species say, angels to triggers? What is the best way to lower the Alkalinity?

 

[malkore]

I'd say a 2.5meq/l of alkalinity is fine for a FO tank, which is about 7dKh.

Lowering alkalinity usually is not a problem...it's keeping it up.

 

[robocop]

Ok...how do I lower the AKL? Say I have a 30gal FO with a 11dkh AKL

 

[malkore]

honestly, I don't have a better option than using R/O water instead of tap water. Most salt blends, even Instant Ocean, will make good R/O water have an alk of 2.5-3.0 meq/l if you're mixing at their recommended levels (IO is 1/2 cup per gallon, 1.021 SG).
That's why I'm assuming you're using tap water. If you're using R/O test it's alk...it should be next to nothing...if it's not it's 'bad' R/O...the resin cartridge is old and needs to be replaced.

I'd test your water first though (the source water). See what it's at. If it's a lot lower than 11 dKh, you might just be building up alk over time. Only H2O evaporates...the minerals that are alk and general hardness remain behind. Topping off with mineral rich tap water adds more hardness over time. Thus you concentrate them. R/O water should be mostly void of any minerals, and thus topping off with it will dilute the hardness.

If that's what's happening on your end, you'll need to do lots of small water changes, preferably with r/o just for the stable alkalinity. Then once it's back in check, you can just do top-offs with R/O.

 

[robocop]

I actually have a RO/DI unit....tested it like you said and everything is ok with it (it tested zero akl) Not sure why the Akl is so high though. I use nothing but RO/DI water. I'll try the water changes as you suggested. Thanks.

 

[malkore]

limestone rock in the tank? not adding any extra buffering?

 

[steve-s]

Ok...how do I lower the AKL? Say I have a 30gal FO with a 11dkh AKL

11 DKH is actually not harmful to the tank as long as the Ca is in balance against it. Alkalinity can be as high as 4.5-5 mEq/l (12-13 DKH) without much stress to the inhabitants. There is no reason to bring the levels that high artificially though. You might consider testing a newly prepared batch of salt. IME, that's where your problem will lie if any, especially if using IO salts.

Cheers
Steve

 

[robocop]

No limestone or buffers.