Q. I have just added a filter to my pond about three weeks ago. Most of the water (which was green) was replaced by fresh spring water although some sediment remains on the floor of the pond. Shortly after, a layer of scum and bubbles appeared on the surface of the water. Each time the scum is removed by adding more water from the spring and allowing the pond to overflow, it returns after a day or so. The EasyClear filter foams have been cleaned and the pond water tested for Ph value, Ammonia, Nitrate and Nitrite. The water tests clear on all counts.
This is the first time I have installed a filter unit and I expected that the water would be crystal clear by now so I would appreciate any advice or suggestions you might be able to offer. Otherwise, I am at a loss to think what else I can do.

A. The scum or oily layer on the surface of the pond is quite common and usually comes from the fish food or natural fallout dust and debris in the air, it is also common on a new pond and new filter as the good bacteria has not built up yet in the pond and in the filter. It takes 3-6 weeks for a filter and or pond to build up enough bacteria so do not over clean the filter and only ever wash the foams in a bucket of pond water never tap water as the chlorine in tap water kills off the bacteria.
If the water tests okay then don’t worry about it, it all takes time just leave it alone to mature. A pond takes three years to fully mature and you cannot rush it. If the water has a slight cloudy or smokey look it is probably a bacteria bloom caused by the nutrients in the spring water again leave it alone and the bacteria bloom will eventually die off as it uses up the nutrients. Every time you are adding fresh water you are topping up the nutrients and feeding the problem.
The worst thing that you can do is be impatient, give it time and leave it alone as long as the water tests okay and the fish are healthy don’t worry.
Overfeeding is another cause especially if the pond has just been set up and running. Feed once a day, only enough food that is all eaten in 3 minutes. If any food is left net it out and reduce the amount of food that you are feeding, as any uneaten food will sink and break down feeding the bad bacteria and cause the ammonia to spike.

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