Backyard Aquaponics
A place to discuss aquaponics

Well a week after dousing with 50ml of H2SO4 (35% Battery acid) the pond looks clearer, nitrates are up, even the plants look slightly better or is it my imagination?

When I used HCL to lower pH it would bounce back up in a week, after the H2SO4 it seems to have stabilised? time will tell.

Probably some what of an allusion... as your previous substantial HCL addiitions had consumed most of the carbonate buffer...

Ph is logarithmic... so as the carbonate buffer is consumed (and pH drops).... it's less likely to "bounce" back.. and requires less acid addition to achieve a pH drop...

thanks Rupe, for snuffing out the glimmer of hope.

When it was a pool it had tonnes of HCL added, 250 - 300 every week or 2! the pH was always rising.

I don't understand the snuffing out the hope... aren't you trying to get the pH down??

You are achieving that... and continuing will drive the pH further down...

The point I was making was that you'll need progressively less acid.. to achieve the same level of pH drop.. as the carbonates are consumed.. and pH lowered..

Sorry I read that wrongly, was hoping I had found the magic bullet.

The snuffing of hope may be more due to the fact that the plaster, having most of it's carbonates used up and if the pH becomes easy to keep down below 7, may start to crumble. I don't really know of sure on that but it would be my fear that if the plaster is no longer tending to elevate the pH then it might not be very stable anymore.
Of course if you have also adjusted what water source you are using, keep in mind that the source water used for a system has a huge effect on system pH.

And if your plants seem to be looking better, that is probably no illusion. The plants do find it easier to get all they need when the pH is lower.

Is it possible after 15 years that the plaster would loose its carbonates?

I know when I need to clean the cement off my levels I use a h acid bath and it eats the cement off in front of your eyes.
I wouldn't have thought It would do anything to a pool with that much water though

some of the plaster is flaky but only in the dry area, I put this down to a bad job of replastering.

Soon after they had done it 15 years ago, burn marks could be seen on the plaster finish, I found out later that this was caused by over working the finish.

Makes you wonder if using a liner might take away what could be a long battle? I hope you get it sorted mate

I don't really know the answers about concrete and plaster and how best to use it with aquaponics.
I know that some people have built systems by making beautiful concrete tanks and the systems have been fine without the pH issues and I've never been able to get them to divulge their secret to keeping the concrete from being a pH problem.
Other people I know have had ongoing problems with the concrete. Some pool paints or potable water paints can be used to seal up concrete and plaster and make it ok. Other sealants can be a problem.

My best guess about what will be the least problematic is to get a high quality liner installed asap.
If you can reasonably pump the water into another tank and catch the fish and move them to that tank (and keep filtration up to the temporary tank while you clean out the pool and install the liner) then I expect it will work better to move the fish and drain the pool to install the liner.

I ordered the liner today. 8m x 9m x 0.5mm LDPE.

you are right TC best to get some loaner tanks and transfer fish and yabbies.

The liner will cover the whole base of the pool up to about 1m depth, so the GB and everything will need to come out.

Thought I was seeing stuff in my FT, then it dawned on me.

Baby fish, those big fat Gold fish must have been pregnant (or whatever the correct term is).

Congrats, Slowboat, you are a Dad!

Prego, knocked up, many buns in the oven...