When was the last time you mucked out the bottom of the pond?

Not for at least 5 years. Btw, this is not a fish pond, though i do have 1 fish in there, and seasonal frogs & their numerous tadpoles.

I usually recommend that sort of pond be mucked out every year. Especially when you don't have a surface skimmer to pull out leaves and stuff before it falls to the bottom to decompose.

With regards to the fountain, having the intake on the bottom is probably your main problem. I'd put it on some bricks. Depending on the size of the fish, if you only have one in that sized pond you probably don't need the tiny amount of extra biofiltration that you get from the filter pads. Now of course if the one fish is a 2 foot koi.....

You could always get a pond vac so you don't have to drain it to clean it.

The goldfish is about 4" in length. I never feed it. It seems to be fine, has been there for 5+ years. The pump + filter is on a shelf, about 10" below the surface of the stones. I do have a fair amount of string algae that i pull out by hand a few times a be week. I also have a pond vac that i use a few times a month, but only on the shelf. I don't vacuum all the way to the bottom of the pond because i know for sure that it'll clog, due to the water lilies and other aquatic plants i have in there. So, given that the pump and intake is on that shallow shelf, do you still think that I'll be ok not using the 2 sheets of filter?

Thank you!!

I wouldn't take the pads out until you get the string algae under control (string algae can kill a pump pretty easily) and you're not going to get the string algae under control until you get the nutrients that are feeding the string algae out of the pond. That means mucking out the bottom because the decomposition of the plant matter is where the nutrients are coming from.

Are the plants in net baskets or just planted in the bottom?

The plants were in baskets when i planted then, but I'm sure by now some have rooted outside. Ok so at least now i have a plan: I'll pump out all the water, clean up all the sediments, and refill with new water. What's the best way to make sure all the string algae are dead? If i let the pond dry out for a few days, will that do it? Btw, I do have a net that i place over the water to catch as much fallen leaves at I can during the fall season.

String algae spores are pretty much everywhere. The best you can hope for control, not eradication. So don't let the whole thing dry out. That will just kill all the good bacteria living on all the surfaces inside the pond. If you take out the fish, you could use algaefix to kill off as much of the string algae as possible before draining. The dead algae is going to use up a lot of oxygen as it decomposes which is dangerous to the fish even if the algaefix is fish safe. Then once it's dead you can muck it out with the rest.

Once the pond is cleaned out, I'd clean up the baskets and put them on risers like bricks to keep them off the bottom. That will make the bottom easier to keep vacuumed when you notice detritus building up. Some people like a bit of detritus for little insect critters and such but too much can quickly become a problem.