getting rid of aragonite sand grains with acid?

[astroboy]

A while ago I had Eheim Substrat (balls made of sintered glass) at the top of a remote deep sand bed. After a discussion on WAMAS where the consensus was that the balls, or any sort of bio ball, would tend to act as a nitrate trap I removed them.

 

Now, I'm setting up a freshwater planted tank for which the substrat balls would be very good to have for filtering. However, all the little crevices have tiny particles of sand in them, than no matter how much I rinse or scrub, still wind up on the bottom of the filter. This is bad, since I need soft water and dissolving aragonite will be a disaster.

 

I was thinking about putting the balls in a muriatic acid bath for a bit. Does anyone know if that would be sufficient to dissolve the aragonite grains?

 

Thanks!

[Origami]

Hi Mark. Muriatic acid should readily dissolve aragonite. Be sure to dilute the acid first. I would dilute at least 10 parts water to 1 part muriatic acid in this case. Remember to add the acid to the water, not the other way around, and to stir as you add it. Also, be careful not to breathe too much of the fumes coming out of the muriatic acid jug (it's chlorine gas and can be very irritating and damaging to tissues). Put a powerhead in during the soaking and it'll help things dissolve more quickly.

[Steve175]

It will work and it will work quickly. Make sure the bucket is not too full of water before adding the muriatic as it will foam up considerably (like a dark beer being poured) and make a mess on the floor. You will not need more than a single gallon (likely less). Agree with 1:10 dilution to start with a bit of water movement.

[astroboy]

Well, I tried removing the aragonite with a 10:1 dilution of muriatic acid:

 

Good news: it removed the aragonite grains very quickly.

 

Bad news: it also eroded the Eheim Substrat Pro filter media. Apparently whatever holds the substrate balls together is also dissolved by strong acid. If I have left the balls in the acid mix overnight I'm sure they would have disintegrated completely.

Edited December 16, 2012 by astroboy

[Steve175]

If they really are glass balls as you intimated, they would be u naffected by muriatic

[Origami]

If they really are glass balls as you intimated, they would be unaffected by muriatic

If it was a conventional silicate glass, that's true. Apparently, that's not the case and, instead of being conventional "glass" as most of us know it, they're using the term "glass" in the broader, technical sense of the word, a non-crystalline amorphous solid. I hadn't even thought that was a possibility when you described the material as "sintered glass," but apparently it's the case.