Hi to all
Can someone tell me what this is and what to treat it with.

David,

it is Papillomas.

Also read: Carp Pox

http://southafricankoi.11.forumer.com/viewtopic.php?t=191

I agree with Pieter, it is papilloma. Carp pox is a white waxy lump, and so is Papilloma, but Papilloma can also be redish/pinkish.

It is a virus which will disappear if you increase the water temperature and it can be removed surgically, but I won't, except if it breaks open and develops infection.

It will dissappear in summer, and migh come back next winter. They normally outgrow it with time.

My pond is not very deep. I would like to now if I can install a few solar
Panels to increase the water temperature.

Large initial capital layout. Is it really worth it?

You need warmer temperatures when the sun is not shining anyway. You can have battery banks with an invertor and heater, but it is expensive.

A solar geyser is an option, but once again, at R 6000.00, is it really an option?

A heat pump will be more economical.

A cheap option is to run your water through irrigation pipes on the roof, but you need a strong pump and will loose water flow. Once again, it will increase the temperature when you do not really need it. However, it is an option if your pond is in the shade.

The temperature in SA is never so cold that it justifies a heater.

Rather spend the money to increase your depth.

I agree with Paul, too expensive.

If you have an air pump to assist you with the oxygen supply, you could cover the pond with a plastic sheet. It will help a little bit