"Keith" wrote in message ...
Not answering your question but wondering if using hydrochloric acid is safe
given that it will liberate chlorine in your aquarium?

That is a valid and logical concern.

I wouldn't have considered this, except that phosphoric acid, the most
commonly-used pH reducer, was totally unacceptable. With my tapwater
so alkaline, I had to use a lot of it, which was both expensive and
turned my aquarium into an algae tank. Phosphorous is well known to
cause algae growth.

So I did some research on alternatives, and found references to
hydrochloric, sulfuric, and acetic acids being used. Hydrochloric
acid seemed to be the best of the bunch. This quote, borrowed from a
couple of Usenet posts from Uareptigrl sums up the general opinion of
what I found nicely:

"All fish are sensitive to chlorine, but hydrochloric acid is a
solution that is safe for fish because the chloride ions are free...I
work for one of the largest aquariums in the world, and we use
hydrochloric acid ONLY. NEVER use sulfuric no matter what the idiots
at the fish stores tell you. Muriatic acid (hydrochloric) is the only
option."

In addition, it is also regularly used to lower the pH of ponds, so I
took the "chance" and never looked back. It works perfectly, with no
detectable ill effects.

Some months later, I brought up the topic with an aquarium old-timer
at a local franchise pet store (a rare and wonderful find!), and he
said that hydrochloric acid was what most people used before
commercial pH reducers were sold.

Advantages:
1) Doesn't contribute to algae growth.
2) A gallon, readily available for $6 in the pool supply section of
the grocery store, is a lifetime supply for a casual aquarist.

Disadvantages:
1) Phosphoric acid tends to lower pH to a certain level and keep it
there, which is why it's so commonly used. Hydrochloric acid doesn't
do this, and will not maintain pH if you have something in your tank
that is leaching into the water and actively pushing it back up.
2) Hydrochloric acid, straight out of the bottle at 31.45%, is strong
and dangerous stuff. It produces caustic fumes that can burn the nose
if inhaled. I handle it in this form as little as possible. Instead,
I dilute a batch with water, at 1:8 ratio, in a plastic two-liter
bottle and use that. At this concentration, it no longer fumes, and
is far safer/easier to handle.

-Chris