Mosquitoes in ponds & why you should not put sand At bottom of a pond

I received a query from a lady who was concerned about mosquitoes and their larva building up in her pond and then hatching. I received another one on the same da although not totally in line with this one it could be ... you decide

If a pond is well cared for - ie good circulation, good biofiltration and if it holds fish there will be very few mosquitoes at all. Quite simply mosquito larvae are a prime source of natural food in ponds and natural watercourses. The larvae spend 99% of their life beneath the surface - ask any trout fly fisherman and are always at high risk of being eaten.

In my own pond I have never seen any larvae The larvae grow in mud and their bodies stick up vertically in the mud ( people who used to catch bloodworms for fishing knew this and they developed a tool that they would pull through the mud on the bottom of a natural pond. This tool was a kind of knife edge attached to a pole with the knife edge at 90 degrees to the pole. The scything type of action through the mud resulted in the large quantities of bloodworms (larvae similar to mosquito larvae)becoming bent around the knife edge.

The problem ponds as far as nuisance mosquitoes are concerned are those with poor circulation or stagnant features such as barrel features and NO fish. Every pond should have at least a couple of small gold fish if for no other reason but to keep the larvae numbers down.

Planting directly into a sand base on the pond bottom

Not recommended (by the way this would also provide a good place for mosquito larvae to live and hence the link between this query and the first one)

A reader asked if a 9 inch level of sand placed on the bottom of the pond to facilitate planting was a good idea. The answer is NO. Why? This layer of sand over a period of time will become mixed with organic excesses from feeding and the daily toilet habits of the fish. In additon oxygen will not be able to reach these organic products and they will rot to put it bluntly. In rotting oxygen will be extracted from the pond water to the detriment of the other inhabitants of the pond. In addition ...... There will be a build-up of anaerobic bacteria (survive without oxygen). Many of these bacteria are responsible for fish disease problems.

Have you ever lifted a bullrush or similar plant from the margins of a natural pond? If so you will almost certainly have come into contact with the products of anaerobic bacterial action ... gases that stink. The challenge in any pond is to keep the bottom totally clean. This is the reason for installing bottom drains in larger koi ponds especially.