wabash

A few years ago I dug up some terra cotta drain tiles from my lawn, they are 6' diameter and about 14' long. I got inspired so put a masonary blade on my DeWalt grinder and began building a city of stone which was to be the main attraction in my new tank (well, after to the fish). The the stones were fitted and the city was built, I felt like the Egyptians.
I decide to boil the pieces just to make sure they would be safe, my pH out of the tap is already 7.5 but after boiling it shot up to 8.5. If I boiled them once I boiled them 20 times and the result is always the same, a rise in PH.
I gave up so am going out to buy some flower pots today and start cutting and creating again but before I waste all that time I have a Q. Has anyone experienced this rise in PH when using terra cotta pots? I have to admit these tiles I found have been in the ground since the 20's and probably absorbed a lot of crap which caused the rise but I thought I should ask.

Red1313

You could try adding some driftwood to lower the pH back down again maybe?
My water is almost 8 right out of the tap. I've never really worried much about it being changed one way or the other.

wabash

I have dreams of a pair of Blue Rams and hoped the driftwood would get me from 7.5 down to 7, then this problem popped up. I have picked up some flower pots, they are cheap much thinner walled than the drain tiles so it won't take nearly as long to cut them up. I am boiling them right now to see if they affect the PH.
Thx Red

Drew 43920

I am getting ready to boil a Terra Cotta pot for my betta tank. Please let me know what you find out .

prairielilly

Curious for how long/what they were exposed to when they were in your lawn and after you dug them up...any ceramic is porous to some degree and it may have absorbed something which is now leaching out in water. Were they ever exposed to water with dissolved minerals? say rainwater runoff from a tiled roof for example? and what about fertilizers on the lawn?

wabash

They were in the ground for many years and caught runoff from both cedar and asphalt shingles. Probably picked up fertilizer and a few other things along the way so I have scrapped the idea.

I just boiled a couple of new off the shelf flower pots and the PH still went up from 7.5 to 8.0. I am new to this and using a wide range test kit that shows in .5 increments but I do have two test tubes and there is a definite difference when compared side by side.

prairielilly

I google'd terra cotta just to veryify, and I can't see clay with iron oxides changing your pH but I could be wrong. Glad you scrapped the idea of the in-ground ones though.

I haven't kept rams and I'm not sure of their specific requirements, but I did think that most fish could be acclimated to a less than 'ideal' pH provided it remained stable. Lots of fishlore members have used terra cotta pots in their tanks without issue, as well.

Hope you find a solution

Tavel

just for giggles, you could try soaking your little city in a weak hydrochloric acid solution (also called muriatic acid). It might neutralize whatever is raising the pH (probably calcium carbonate (limestone)).

wabash

That would be the solution you were referring to prairielilly?

Tavel, I think you are right, I was trying to find a receipe for terra cotta dough as I think there is limestone in it, same idea as concrete. At this point I have moved on to the flower pots but I will try the muriatic acid just as an experiment. I have used it before to clean concrete off of old bricks so it will be interesting to see what it does to terra cotta.

prairielilly

Terra cotta is ceramic, which in this case is fired clay. It contains iron oxides which give it the reddish orange colour. Clay is altered feldspars +/- quartz and possibly some calcium carbonate (lime) which may have been present in the original clay, but that contribution is minimal. At least that's what terra cotta originally was (+/- some geology).

Unless of course, modern manufacturers have made a different kind of ceramic and just added the iron oxides to it to give it the terra cotta 'look'. In which case it likely does contain much the same stuff, but also more calcium carbonate - which would then account for your pH. Sorry, I didn't consider earlier that modern manufacturing would've mucked with the formula

If this is the case, when you put muriatic acid on the ceramic it will fizz. It might fizz immediately, or it might fizz only if you scrape the ceramic to form a powder and put the acid on that. Any fizz at all, you've got calcium carbonate (and possibly some magnesium carbonate). If this is the case, you could soak the stuff in the acid for a hundred years and it will never 'neutralize' it - but it will eventually dissolve away.

wabash

Prairielilly, can we assume that you are a potter? I guess even if the limestone was neutralized then I would have to deal with muriatic acid residue in the water. The drain tile idea is officially dead and I will start cutting up the flower pots as soon as it warms up a bit.
My buddy drove by when I was doing the other ones. Apparently it's quite a sight, me with those white painters coveralls, hood up, dust mask and safety glasses in a cloud of red dust and the snow red for ten feet all around me.

prairielilly

Sounds like you're having quite the adventure with all this! I'm wondering if you painted the ceramic with a sealant if it would then be waterproof?

I was thinking if you rinsed it a LOT the acid would be diluted enough, but yeah I wouldn't chance it either (your fish are breathing this after all)

Never been a potter....I'm a geologist (and a bit of a science geek too I guess)

Tavel

my neighbors don't even ask anymore...lol.