I've just seen your posts so they're new to me.

First, stop bringing fish into the equation so early. The fish can wait.

What do you want from this aquatic feature? You have to ask yourself this. Do you want care free, (you'll never get that)? Do you want to take care of fish? A water (plant) garden? Both? Are you likely going to be "into" crystal clear water? There's a lot to do to get there, but it can be done.

My water gets there very soon after June 1 when my floating and submerged aquatic plants start thriving in the heat.

Your little pond should have probably been netted in the fall to keep the leaves out. Count on doing that next autumn. There are many ways to making "the system" bullet proof from a debris-introduction standpoint.

For now, get a net with a long, telescoping arm. Work the bottom. This will bring-up, stir-up the fine particles of dirt and debris. Maybe some plants overturned and dumped dirt/clay/sand... that might be one reason for the filthy water. Debris will stay afloat for a long, long time... but keep cleaning those filters. Have a nozzle jet spray close by and at the ready. Clean the filters outside the pond area.

Do you have a biological filter. This is a place (basin) were pumped water is usually returned to the pond. It often has a water fall (weir) feature. If you have one, go get some new clean filter media. New material here is important... sometimes media gets blocked, like lava rocks, LR aren't the best media.

BioFilter: Place the filter media at the bottom and top it with some aquatic plants. This will be your bio-filter. A place for beneficial bacteria to collect and help cleanse your water.

Some aquatic gardners add beneficial bacteria to ponds. A bottled product that can be purchased. You may wish to visit a local aquatic store (not just a pet store) but a pond/aquatics store.

Just don't add fish, for now. They just make the water system work harder and you're not ready for them yet.

Test your water in a week as it slowly clears. Test kits are available online or at aquatic centers.

Read up on water gardening. Try the "The Pond Doctor" to start with... there are also how-to-books (softcover) available at the big box stores that I find to be good reference materials.

Good luck!

Ponds are not drinking water, some sludge, some algae is going to happen. Carpet algae on the liner is good, it helps use nutrients that fuel a pea soup algae bloom.

Keep changing the filter floss and add some plants and have patience, water cycling takes time.

I'm sorry but your pond is too small for koi, unless you are going to give them away when they get too big as the previous owner should have but didn't. His koi would not be dead if the pond was big enough and properly filtered.

Goldfish are easier, require less depth, less filtration, don't grow nearly as big and don't tear up plants which help with water quality. Feeders are often half dead when you buy them so don't judge goldfish hardiness by feeders.

Jeff