I use the same stuff, you can cut it to size and it will not unravel. I have also found it won't last more than one growing season in spite of it being nylon. It might last more than one season for light plants like beans, but for tomatos, zukes,cukes etc it will start breaking near the end of a season. Not so much it collapses, but enough that you won't want to reuse it.

In zone 7 you can run the pump and filter year round with no more than regular maintenance and attention. It is possible your water may get up around 55oF occasionally in spots as it is. I decided to run the pump through the winter 4 or 5 years ago here in zone 5 when my health took a turn for the worse.I have had no problems related to ice dams. Debris and squirrel nests are a different story. There are things that can cause problems. I try to think smart to circumvent them as much as possible. For example, water spread out as in a pretty stair step waterfall is likely to freeze solid so in my pond water from the outlet to the pond from the filter is one straight drop. It freezes but the flow forms it's own tube in the center that is actually protected somewhat from the winds and cold air so the flow is almost as much as it would be in warmer weather. If the force of the flow were reduced it is possible, even likely, that the tube wouldn't form. As it is, there is enough circulation that no ice has ever formed in the Skippy. If it did, I would resort to a deicer on top of the filter in front of the outlet pipe but sufficient flow is essential. Since no two ponds are alike, you may have totally different situations to deal with. Some advantages of running the pump are continued filtration and elimination of "dead zones" where there is a decrease in oxygen, and more consistent temperatures throughout the pond. I think this can reduce the existence of anaerobic bacteria and parasites in the pond although I have no proof except that I rarely have any casualties among the fish population during the winter and early spring that I can attribute to that since I have been leaving the pump running. The amount of crud that accumulates in the filter certainly indicates that it is improving water quality. Cleaning out the filter is about the same as replacing it at any other time. Water changes don't seem to be really necessary except for leaves and other debris that got through the netting. Since the end of the prefilter in my system is at the lowest end, most of the organic matter rotted from the leaves has been carried to the filter. What remains can be vacuumed up which does a partial water change. If there is too much of this degraded leaf material or a stray piece of plastic or other debris it can clog up the prefilter. You want to keep an eye on that. It puts a strain on the pump. I replace the Activated Carbon and Ammochips as I replace the filter material unless I need to medicate the pond for some reason. Some people use some version of commercial bacteria at this time. I don't. I just save a scrap of the old filter material and leave it in with the new material for a week or two until temperatures level out. If I had problems with parasites I wouldn't do that since eggs and larva could be in the old material. One thing that can calm your nerves is a wireless submersible thermometer. There are some nice inexpensive ones on the market that allow you to keep an eye on the water temperature from a distance. When you start feeding the fishies it is easy to overdo it. A couple or three feedings a day rather than one is much better for their digestion. If your pond doesn't support algae, you can even drop in a few algae tablets made for algae feeders and your fish will love them. I haven't seen these encourage any algae growth and they are easily digestible for the fishies.

I'm not familiar with that netting, but if you do have to burn the cuts, cut/burn them with a small soldering iron. It will cut and seal them at the same time. The El Cheapo ones are about $5. Sue Here is a link that might be useful: El Cheapo soldering iron

You can... and imho should.... periodically remove the debris from the bottom and clean the filters without destroying the bacteria. Just dont scrub hard and dont use any chlorinated water, or any type of cleanser and certainly not bleach. A bucket of pondwater and scrub brush work fine. if its matala pads just bang them on a rock to shake out the sludgy stuff. You want to keep the filters clear so that they dont plug up and block the flow and so that they can keep filtering out the fine debris. Bacteria also live on the walls of the pond and in the tubing so periodic removal of debris is not going to harm anything. Fish helping to clear layer of dirt and debris??? That makes no sense at all -t hey are not going to eat it, only contribute more poop (ie organic matter). If the pond looks reasonably clear and tests well now with all the organic stuff in it, that will definitely change with the addition of fish and their waste to your bioload. Glad to hear youll only put in 2 koi bc thats about right, any more would be too many. The guy who gave you that advice - I wonder if its an Aquascape store bc that is a particular method of ponding that relies on using their products and using their chemicals at particular times of the year. Guess it works for some people, but the problem Ive found isif they seem to be unaware of other methods of ponding and make these pronouncements that can have dire consequences if you arent following their method or have adequate equipment/filtration. Almost killed my fish once following their advice which was to just ignore the build up of debris and nitrates and just use one of their sludge removal products .... once I got a clue and put in adequate bio & mechanical filtration ev has been just fine.