There is a fountain which works when switched on from the house. This works. Is it good for the fish apart from being decorative?

There appears to be provision for a small waterfall coming from a pipe in a mound of rocks. This does not work. Behind the mound of rocks is a box which I presumed was some kind of pump. I took off the lid and see it is full of wet mud with a pipe visible at the top. Is this a pump or a filter and should I remove all the mud. I cannot see how the electricity is connected to either the fountain or the filter/pump box.

Also I noticed that one of the small fish kept wriggling onto the top of the pond weed which is quite thick at one end of the pond. I thought it was stuck but when I came near it just wriggled underneath again into the water. I have cleared some of the pond weed (there are two lily plants and some kind of water iris as well so it is quite well established) but wonder what the fish was doing - need I worry?

I know nothing about fish and have just fed them except for the very cold weather and put in a water heater in the winter in freezing weather so it did not freeze over as it is not very deep (scarcely 18inches). I hope to renovate the pond in the Spring but do not want the fish to suffer in the meantime.Thank you, Lesley

The fountain, apart from looking decorative, can be beneficial to the fish, especially during hot weather as it helps to aerate the water and maintain oxygen levels. The only time you might want to turn it off is during windy weather when the spray might not all fall back into the pond, and so the pond would lose water.

The box in the rockery sounds very much like a filter, especially as it is full of mud! It may well be that the fountain has a 'T' piece connector in it (in the vertical pipe just under the jet) which allows water to be pumped up to the filter box. Here, the water would trickle through probably some form of sponge material to strain out the dirt from the water and then the water returns to the pond via the pipe you see sticking out of the box.

There must be an inlet pipe to the filter box – it might also have a tap or valve on it to switch the filter off for maintenance purposes. It might not have been turned on again last Spring?

Certainly there would be no harm in cleaning out the mud, if only to see what's underneath! If the sponge filters have not disintegrated to any degree, they may be put back into the filter for re-use.

Without going into too many technicalities, after a filter has been cleaned it will take a few weeks to return to its full efficiency again. Subsequently, when you wash out the filter medium, you should do so using some water taken from the pond so as not to totally destroy any beneficial cleaning bacteria that the filter sponge has living in it. For this first clean-up, don't worry too much about using pond water, as there is no water coming out of the filter it is obviously not working at the moment and so there won't be too many bacteria to destroy.

Turning to your fish, I think that it probably wriggled up on to the water plants during the excitement of spawning, and being chassed by a male fish. Alternatively, and you did say it was a small fish, it may have been chasing some surface dwelling insect and just overdid things a bit.

As far as caring for your fish, I think you're doing all the right things (even if you don't realise it at the time). Don't feed the fish at all once water temperatures remain consistently below 10 degrees Centigrade. They will not need feeding and any food left uneaten in the pond will pollute the water to sore up algae problems next year and if the fish do take in food they can't digest it at these low temperatures and this again leads to health problems later on.

It might be a good idea to get some of the silt (if any) out of the pond this autumn rather than leave things until next Spring. Cut back all the dead water plants too, as any decomposing matter in the pond also can cause trouble next year.