Pond biofilters, solar power and ponds

Pondkeeper's How to...

Solar power and ponds

Only have solar power and a biggish pond is what a reader reminded me of. 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.