New tanks in the tosai house

When we first built the tosai house back in 2006 we got it up and running with some temporary tanks that were basically a sheet of steel that formed the walls of the tanks, and a liner. Once filled, the water kept the sides of the tank rigid. They were a great way to get us going without too much expense but this year we decided to replace them all – prompted, it must be said, by the first tank that Mark filled up after the summer actually bursting in a great tidal wave of water at 10.00 pm one evening whilst he was stood next to it turning off the tap!

We needed something that was going to be permanent and were happy to replace them with something similar but bearing in mind we had six 2000 gallon tanks to build, once again we had to find a cheap and effective way of doing so. We came up with the idea of building them in the same way that the original steel pools had been made but instead of using a sheet of steel and a liner, we would make a sheet of fibreglass that would form the walls of the tank and then line that with more fibreglass.

We needed something to lay the fibreglass onto so Mark ordered some lengths of PVC and laid them on the floor of the tosai house.

All laid out

The fibreglass was then laid in strips onto the PVC and the resin applied with a roller. After setting, the sheets of fibreglass were rigid yet flexible enough to be curved into shape.


Each tank then had a length of hosepipe attached to the top rim to give it extra strength and a smooth edge for us to lean on when sorting fish.

Hosepipe Attached

Mark then put tape over the top of the tank and hosepipe and fibreglassed over it, giving it extra strength and making a smooth finish.


After finishing the top of each tank Mark then added a layer of fibreglass to the floor and sides making the whole tank water tight and adding greater strength. After that it was just a case of leaving them for a couple of week and then filling them up and adding fish.


Job done!

I’ve never seen this particular technique used before but it’s working really well for us. Most Koi ponds are rectangular or square but most tanks used in aquacutlure the world over are round, simply because it’s the most efficient shape for the ciculation of water and the removal of waste. Anyway, just thought I’d share it with you.