I use fish boxes too :) but I use them as the internal recess for my planter i.e I get a bigger box which is 5 cm bigger then the fish box on all sides. I place the tufa mix between the fish box and the bigger box. Once it dries I can chip away at the fish box and I have a smooth trough.

Thank you so much for your response.

I was hoping to reuse the fish box a few times and not destroy it if at all possible. Will lining it with plastic bags save the fish box?

What material/s do you suggest for the outside framework?

Thickness of hypertufa mix for sides and bottom - will 3" be strong enough? I have managed to get some fibreglass to strenghten the project. How much should I use? Will one handful per gallon mix be adequate?

Thanks again.

Here is a link that might be useful: themes

If you want to reuse the mold, take a little extra time a make it out of plywood. Cut 1/2 plywood to size and then cut a 1x2 board and screw along the edges of each board and then can use longer exterior screws to assemble and unassemble. It will last forever and it is easy to make.
Use 2" builders Styrofoam insulation (4x8 or if you can find 2x8) for the inside of the mold. Cut with sharp serrated knife. Sorry I have no pictures of the wooden molds but I if you check out the post called "A Sedum for all Seasons" you will see the large Hypertufa container that I made.
Avoid kitty litter - if will break down over time and may absorb water , and it NOT light weight.
Use perlite - it is very light and you can buy large 3 cubic ft bag at a nursery garden center for a reasonable price.
I use reinforcing fibers found at a concrete supply store to help hold together better.

Mike

Here is a link that might be useful: Garden Design Ideas

i cut 4 pieces of malamine wood so when joined in a cube would be 5 cm bigger than the fish box on all sides. To make life easier I joined the malamine with hinges...so it would be easy to remove without damaging the tufa in the process. I have 3 hinges on each side as the weight of the tufa mix is substantial. One occasion I made the mix a tad to watery as an experiment to see if this would make life easier....it did not not. The hinges gave way and all the mix went everywhere! I managed to redeem it just in time thankfully. Oh and I built the pot upside down I.e the fish box was at the bottom of the cube and :I put the tufa...afterwards I turned the box once it dried. It was extremly heavy. I put some hosepipe tubing above the fishboxes to the top...this would act as drainage holes so I can put plants in it.A pic before I turned the pot the right way just after I removed the hinges.

This post was edited by themes on Tue, Dec 17, 13 at 17:54

turned it the right way

then decorated it

Nice Paris in that Link Mike. Is it Paris Polyphylla?

Thank you so much for the advice and ideas.

I shall post the completed projects if successful!!!!!

Themes, when you decorate, do you use hypertufa or cement or some adhesive to join the decorative pieces?

cement and sand 50 50 ratio with sbr added. i also ensure what I am bonding both are thoroughly wet. Once I have stuck them I add plastic on top to slow down the drying so the bond is stronger. All in one piece is always going to be stronger though