Are koi vegetarians? Why do women catch the biggest salmon?

Another very interesting question came from Carol McKnight. Here it is

Mr. Roocroft, Our koi are eating the roots to our floating plants. We have seen a local pet store place cut zucchini or orange halves into the aquariums of koi. Do you know if this is safe for the fish to eat? Also, I would like to thank-you for you're reply to another question we had earlier about the red worms.

Koi are evolved carp; and carp are definitely vegetarians, in fact they are omnivores. There is a special kind of carp sometimes used in larger lakes to clear the lakes of weed growth. They are called grass carp and they grow quite big.

Back to zucchini and oranges. Many koi keepers feed oranges to their koi ... I used to sell by the way an orange flavoured koi food .... They also feed them cabbage, lettuce and most other vegetables.

Like most things feeding such items is best done in moderation. It is safe to do this.

Koi are great destroyers of pond plants for this simple reason and it often pays to cover the top of plant pots with stones to prevent severe attacks.

Carp fishermen are well known for their "secret" baits which they swear buy. The principle is based upon smell normally since carp and koi have tremendous ability to pick up small traces of odour in water. This leads onto another story.

The biggest salmon ever caught in the UK was caught by a fisherwoman and there have been many other instances of large salmon having been caught by women. The theory (I find it hard to believe personally but why spoil a good story) is that women catch bigger salmon because of the pheromones (scent chemicals) unique to the female of the species and it is these pheromones that attract the fish.

3. How a correctly designed biofilter can save you money on a pump

I am sure you are saying to yourself how on earth can biofilter design effect the cost of a pump?

Here is the relationship between a biofilter and the pump. If you have a biofilter with lots of bio media inside it then you need lots of water flow just to cover the bio media.  If you need lots of water flow then by definition you need a larger size pump.

If you have a small flow of water to a larger biofilter than the following happens.

The water finds its way down certain parts of the bio media and not others.

This is typically what happens in a sand filter but it can also happen in any biofilter with any other bio media where water flow is insufficient to cover the media. This is called channelling.

In anaerobic areas of the biofilter where water flow is insufficient two things happen.

Any bacteria in those areas will be devoid of oxygen and will die

Anaerobic areas within a biofilter breed anaerobic bacteria which are potential disease problem sources.

You can see then in principle that the smaller biofilter made possible by using efficient bio media can have smaller flow rates through it because it is easier to ensure water flows across the complete bed of bio media.

Because of the above reasons it is always better to have a biofilter were the water flows up through the bio media.

Please note despite the above discussion it is always a good idea to pump sufficient water around the pond to change the contents approximately 8 to 12 times a day.