Seal concrete block tank?

[Josiah Sherman]

Hi to everyone, this is my first post

I live in central Texas and I'm building an aquaponics system. I started by building a concrete block tank and then built a greenhouse over the tank with lots of space for grow beds. When I originally built the tank I didn't realize that I would need to seal it from the concrete. I have now learned that the concrete block has a very high pH and will hurt the fish and plants.

I have looked a little at SanitTed PermaFlex and Epoxy Paints.

If anyone have tried these product or if you have used another product that has worked well, please let me know.

I include a picture of the tank and greenhouse. Thanks!
Josiah

[Josiah Sherman]

I really like the Thoroseal idea!

Just wondering how smooth is it when finished? I'm thinking I may use Thoroseal, then paint it with Epoxy Paint.

What do you think?

[Bob Campbell]

If you use a brush it will be rough like 80 grit sand paper.  You could trowel some mortar over the Thoroseal to make it smooth, but it's really not necessary to do more than just brush it on

Josiah Sherman said:

I really like the Thoroseal idea!

Just wondering how smooth is it when finished? I'm thinking I may use Thoroseal, then paint it with Epoxy Paint.

What do you think?

[Josiah Sherman]

Thanks, I start will this information and let you know how it goes!

[Jon Parr]

Bob, does the Thoroseal also affect your pH? I thought it was still a cement product, I'll look it up. Cement is actually fine for fish once it has cured and seasoned a bit, as most fish prefer a higher pH. The plants don't, however. What is the pH of your koi tank and do you do anything to control it?

Josiah, your deep tank may be a candidate for pumping water with an airlift style pump, more efficient and more reliable. The maximum lift is a dependent on depth, so plus there. Plus you can practice freediving!

[Josiah Sherman]

Hi Jon,

I also had heard that the Thoroseal raises the pH, so please let my know what you find out about it.

I have never heard of an airlift style pump, do you have a link or a good place to purchase one?

Thanks for the tip!

[Jon Parr]

Thoroseal site says it is not suitable for pH below 7.2, so no good or AP.

http://www.basf-cc.ae/en/products/WatertightConstructionSystem/Thor...

Interesting that they recomend a 12% salt rinse to neutralize alkalinity. I wouldn't have thought of that. Josiah, I would imagine that Thoroseal would pH stabilize over time, but likely not below 7.2, which again is great for fish, and not terrible for plants. However, most plants will be much healthier and nutrients will be more available when pH is closer to 6.

Another thread mentions someone sealing concrete with paraffin, or bees wax. Or pool plaster with a penetrating acrylic sealer.

I'll look for info on the airlift pumps. The principle is very simple. Just drop a pipe to the bottom, and release a stream of air at the bottom of the pipe (bubbles inside the pipe) The rising bubbles create a current which will actually pump water higher than the surface, as well as adding to aeration. Different depths, pipe size, and air volume will create different flows. And no submerged pump to foul or maintain.

[Vlad Jovanovic]

Section 4.3.5.2 gives a good run down on airlifts and how/why they work. Some of the basic principles, and more importantly concrete working proportions expressed in mathematical terms (as well as diagrams)  in case you want to mess around...The rest of the document is nothing to sneeze at either :)

http://www.backyardaquaponics.com/Travis/Aquaponics-Design.pdf

[Chris Smith]

I used paraffin wax to seal my ferrocement tanks. The water now beads off the walls. It eliminates any pH issues since the water never comes in contact with the concrete. I melted it in an old pot and brushed it on. Then heated it into the concrete with a wed burner and applied another coat.

[Josiah Sherman]

Hi to all,

Thanks for the posts and links.

 

Jon, Thank you for looking into the Thoroseal, Do you think if I painted it with epoxy paint it would remove the pH issue?

 

Hi Chris, what long have you been using the paraffin wax? Has it seemed to hold up well? How big is your tank?

 

Thanks,

Josiah

 

 

[Bob Campbell]

Another thread mentions someone sealing concrete with paraffin, or bees wax. Or pool plaster with a penetrating acrylic sealer.

Just remember, once you paint with epoxy or seal with paraffin you have placed a substance on the tank that will not readily adherer to more mortar or Thoroseal.  I had no problems and did nothing more than rinse.  I suggest rinsing and following the directions from Thoroseal.  Then test the water and determine if further action is required before committing to a second layer.

[Bob Campbell]

My water comes out of the ground a PH 8.0 and the pond is always at 8.0.  So I don't think it is affecting the PH.

Jon Parr said:

Bob, does the Thoroseal also affect your pH?

[Chris Smith]

I have a 1000 gallon fish tank and a 600 gallon sump both made out of ferrcement. I sealed both with paraffin about 2 years ago. I have never had any issues with the sealing job at all. My method of heating the wax after painting on the first coat causes the wax to be absorbed by the concrete. This will fill any hairline cracks and make a waterproof barrier between the concrete and water. A second layer of wax will help insure coverage. I have used this technique on many other concrete and block tanks since.