Hi Marius - thanks for your reply re the pond cracks!
It appears as if the previous plaster had no salt and hence the plaster is cracking off the concrete structure! (The builder informed me that it is due to the koi sucking algae off the side-walls???) -which sounds ridiculous!!One further problem is that I have two holes where the bottom drains should be. The holes are approx 110mm but have no covers as such - simply holes with outlets to my filter. Where would I obtain the domed drains that would fit flush?
Have u heard of Viresco and would u recommend it for algae!

many thanx
Rick Borain

Hi Rick

Yes, I agree it is ridiculous for Koi to suck the plaster off. Maybe a new breed????
I don’t know where you stay but there are many Koi shops selling drains. I use two 110mm drains in my 30000L pond and they work very good. Got mine from Builders Warehouse they look very much like the normal domestic covers. I will send you a PM with some sites where you can find these items. Just remember that the covers must be flush with the bottom of the pond to work properly.
It is easy to clean your settlement chamber if the drain pipes are vertically. All you need to do is to fit a separate pipe on top of the drain pipes that is higher than the water level. Now no water will enter the chamber and you can flush it. After cleaning simply pull the loose pipes out. The ‘pulling’ effect of the water will clean out your drain pipes at the same time.

Regards
Marius