Concrete Pond Construction

Q. I knew someone who had a display pond for coldwater fish in an aquarium shop. A builder built the pond from concrete blocks, then painted the interior with Aquaseal 40. Is it recomended to use it straight on to the blocks?, must you render it? or under what circumstances do you think this is acceptable.

A. I have never heard of painting Aquaseal on to the blocks directly. The instructions say it should be applied to a smooth surface. I would consider it important to render the surface first, and include waterproofing in the render. Some of our members did use a substance called Brushcrete which could be applied directly to the blocks, and this is still satisfactory after several years. I don't know where you can buy it, but it may be worthwhile trying some larger builder's merchants.

Q. Do I need to waterproof the cement pond? If yes, what is the product?

A. Yes, as described on my pages it must be waterproofed, and should be added to the top coat of render. If you purchase the cement from a large building merchant then they should be able to supply the waterproofing which comes in liquid form. It is the normal product used in the building industry.

Q. How much fibromix should be added to the top coat of render?

A. The top coat (about 5mm thick) should consist of the following: -
4 buckets (2 gallon size) sand.
2 buckets cement.
1lb fibres (1/2 bag).
The sand, cement, and water are first thoroughly mixed then pull the fibres apart, and add them uniformly to the mix. If you add them in one lump they will not mix correctly. Fibres are not liable to damage by extended mixing.
If you are using a cement mixer then wash it out very quickly as once it starts to go slightly hard it will become very difficult to remove.

Q. We are having difficulty sourcing Fibromix through our Builders Merchants. If possible could you please answer the following questions-
1). Is Fibromix the correct name or is there a trade name?
2). The name and address of the manufacturer if known.

A. You should have no problems in getting it from any of the larger Koi dealers.
The product is also known as REIN Fibres, and this is manufactured by REIN LTD, Clifton Hall, Ashbourne, Derbyshire DF6 2GL Tel: 01335 342265 Fax: 01335 346664.