Two queries about solar energy in terms of pond keeping

Solar pumps with capacity

I got two queries about solar energy in terms of pond keeping last week so I thought it might be beneficial to provide my thoughts on solar energy in a pond environment.

The concept is great especially if you live in sunny climates like I do in Johannesburg (my queries were from Hawaii and California by the way) but if you live in the UK type of average climate such products are probably not for you.

Even in my type of climate my experience with a fountain pump was very poor. The first query I got was asking for advice on solar powered pumps with "humph .." or power. To the best of my knowledge powerful pumps in terms of head or volume are just not available. The reason is the largish amount of electricity required for such an operation.

Solar power is capable of supplying the power ... you just make sure the panel collecting the sun's rays and converting this into electricity is big enough.

However the problem arises when the sun sets. Power generation stops and unless you have a very large battery (charged during sunlight hours) any equipment will stop working. A battery with sufficient power to run a pond pump delivering say 500 gallons per hour would quickly use up the power stored in a small battery and that assumes the device came with a rechargeable battery in the first place.

Solar equipment with rechargeable batteries do exist but the cost for most pond keepers would be prohibitive.

This first query lead onto a far more interesting one from Hawaii. This reader lives in a remote part of Hawaii and had already built a fairly large pond before he bought my book. Only have solar power and a biggish pond

When the reader read my book he noticed very quickly my stance on biofilters for fish ponds .... ie they are absolutely essential. He had a dilemma because he could not run a pump to feed the biofilter 24 hours per day for the reason he relied totally upon solar energy and an emergency generator.

He contemplated filling the pond in because he wanted to keep fish as well as plants. He had built a pond of about 5,000 gallons (20,000 litres). In the case of this situation the inability to install a biofilter was best overcome by the following advice .... which does apply for a smaller pond too.

However it is NOT a substitute for a biofilter in small garden ponds.

DO NOT FILL THE POND IN ... you can still enjoy it

1. Only stock a few fish at the max rate of about 1 inch per square foot of pond surface. As the pond develops and matures a few more fish can be added. Try to mimic what you would see in a natural pond of similar dimensions.

2. Very important .... do not feed the fish unless done very sparingly and only once a week or so and preferably a small amount over a long period rather than all at once. The food happily fed to fish is the source of many problems.

Fish are able to survive quite nicely on the natural larvae etc that will quickly appear in the pond. They can do this for ever ... the fittest survive just as in nature.

When fish are fed with synthetic food there is a sudden release of ammonia which without a biofilter could create problems ... hence the advice to feed small quantities regularly rather than a larger quantity all at once. The risk is higher in small ponds.

3. The fish should be introduced slowly and not all at once

4. Plants of all sorts and especially oxygenators should be planted as soon as possible

5. If a pump could be run for parts of the day to improve circulation this would help but a biofilter outside the pond would be a waste of money.

6. When or if the pond goes green then be patient and allow the system to attempt to correct itself which it will possibly do if the nutrients added to the pond are absolutely minimised so that the plant material in the pond is sufficient to absorb the natural build-up of nitrates and phosphates.

7. If possible pump out say 10% of the pond volume every week or so especially in the beginning. This will assist reduction of nitrates and phosphates also.

Mosquitoes in ponds

A 3rd query related to the above was from a lady who was concerned about mosquitoes and their larva building up in her pond and then hatching.

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 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.

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.