One strategy for both would be to work with what you have. Around the edge of your pond you could put rocks, not in necklace formation, but thoughtfully arranged to look natural, and interspersed with plants that like the wet area. One way to get ideas on how to arrange the rocks is to go to ponds or waterways where there are rocks naturally and take photos to get an idea of what looks right. Then you can use those for reference. Books on water gardens from your public library may have some nice images that give you ideas as well. There are lots of lovely, non-invasive plants that like wet feet. Some of these are happiest in wettish soil, and some will grow in standing water. You can choose plants for both your wet areas to dress things up without changing the essential character of the area. Two deciduous rhododendrons: rhodora (R. candense) blooms magenta in very early spring followed by blue-green foliage, and swamp azalea (R. viscosum) blooms white to light pink summer and may have nicely colored fall foliage. One evergreen rhodie, R maximum, is moisture tolerant and blooms about now. There are a bunch of selections for flower color, etc that you may be able to find at specialty mailorder nurseries, that might not but most likely will have the same moisture tolerance. Labrador tea (Ledum groenlandicum or Rhododendron groenlandicum) has evergreen foliage and small white spring flowers. High bush blueberry (Vaccinium corymbosum), has flowers, fruit, and red fall foliage Huckleberry (Gaylussacia frondosa) is similar to blueberry. Red chokeberry (Aronia arbutifolia) has white spring flowers, red fruit and fall color, and black chokeberry (A. melanocarpa) has similar characteristics with dark berries. Serviceberry or shadblow (Amelanchier spp.) has early white spring flowers berries the birds love and may have nice fall foliage. Different varieties are from large tree to large shrub sized. Wintergreen (Gaultheria procumbens) make a nice loose evergreen ground-cover with small white flowers and red fruit. Summersweet (Clethra alnifolia) has late summer flowers in white to pink, and many selections. Winterberry holly (Ilex vertcillata) is a deciduous holly that has bright red berries in the fall until the birds eat them. They really blaze against the grays and tans of late autumn and early winter. Red osier dogwood, (Cornus sericea or C. stolonifera) has bright red stems, especially if you cut it back each spring. Northern arrowwood viburnum (V. recognitum) has nice panicle of white flowers, followed by berries if there is more than one variety in the vacinity. White cedar (Chamaecyparis thyoides) is an evergreen that likes wet feet and you can find selections from large shrub to large tree in size. Red maple and Cottonwood will also grow along seasonally wet areas. There are willows ranging from pussy willows to weeping willows that like wet areas. Taxodium distichum, Bald Cypress, is a deciduous conifer that gets huge and is quite striking. Dawn redwood (Metasequoia glyptostroboides) also is a huge conifer that doesn't mind wet feet. Some perennials include turtlehead (Chelone), white to pink late summer flowers; cardinal flower (Lobelia cardinalis) scarlet late summer flowers, marsh marigold (Caltha palustris) yellow early spring blooms, several kinds of gentian, fringed & closed or bottle are two of them, and many kinds of the fibrous rooted iris, like Japanese, Siberian, blue flag. (not Iris pseudacorus, yellow flag iris, which is invasive.) There are several ferns, like cinnamon (Osmunda cinnamomea), Royal (O. regalis) and interrupted (O. claytoniana) that are lovely and like wet feet. A number of grass-like plants like this type of environment as well, including many sedges and reeds. A wet area like this can attract lots of wildlife. We have a seasonal wet area about the size of yours, but which dries up many summers, which has frogs breeding and singing their hearts out now. We have herons and ducks that visit when it's wet, and sedges and reeds that grow there along with some cottonwoods, red maple and pussy willow. I enjoy having it there.

Back years ago, I think in this forum, several members were interested in building vacuums specific to cleaning fish ponds. I was one who got into it. I developed several vacuums and went to several people's ponds to test vacuums in different conditions. Here's my page on vacuums. There's also links to building vacuums. I don't know your pond, but in general, some species of string algae when alive and mature is like horse hair. Bind a little together and it's like rope. I've pulled every bit of out of a pond in one pull and it brought pretty much everything in the pond with it up to the size of a brick. I don't think it would be possible to remove the string algae without removing the hornwort too. Once removed you could try and get some hornwort out of the string algae and replant. But string algae can come back, although often it's another species or it doesn't grow the same way next time. Even if you had no hornwort, gravel or reeds, I don't know of a single vacuum that is effective with string algae. If the string algae is still alive it is basically one plant and in your size pond when removed it could be in the 100-200 pound range. No vacuum can't handle that. I've seen a vacuum with a cutter on the end that's suppose to be able to cut the string algae. I doubt it works, but you should read reviews if considered. Even dead string algae, which breaks up easily is a big problem for a vacuum because of the volume. Easier to remove by hand or a swimming pool leaf rake. For live string algae I used 2 pieces of 1"x1" wood nailed or bolted together in the middle so they would open and close like scissors. I'd make them about 5' long. Open them a bit, push into the algae, close, and then spin them so the algae wrapped around the wood. Once I had a good ball I'd pull it out. Generally every bit of algae came along with this ball, along with anything it was attached to. Different species of string algae and the different life cycle stages can require different methods. I learned 2 basic things. First, there is no single vacuum that is effective. Ponds are cleaned in steps, removing big stuff first and ending with the small stuff. Different tools for each. Second, don't build a pond that's hard to clean. Loose rock, gravel, plants, all good great...until it's time to clean. I mortared rock so it was easy to clean and moved all plants into their own beds and so their crowns were above the water. Crowns above the water = no string algae = happy pond keeper. That means no underwater plants like hornwort and no lilies. Lilies can get their own pond or their own deep water bed adjacent to the pond so the pads can grow out over the fish pond.

The skimmer box can be any size you like, can even be a pond (skimmer between 2 ponds). The width of the weir door (flap) determines the pump size...kind of. Really pretty much any size pump will work with any reasonable width weir. Technically you could compute the amount of water desired over the weir. So say 12" wide weir at 1/8" deep is about 1.4 sq in of water which is about the size of a 1.5" pipe. Looking at a flow table for gravity to low flow (6'/sec) you'd need a 2100 GPH. With 1/16" over the weir a 1050 GPH pump, for 1/32" a 525 GPH pump. Lot's and lots of pond owners, including high end pond owners, believe, and will always believe, that the bigger the pump the more "powerful" the skimmer. I've also seen many posts from "experts" saying a waterfall is needed to push debris to the skimmer. That all ignores the physics of why a skimmer works which is based on surface tension. The thinner the water going over the weir the stronger the surface tension pulling debris into the skimmer. So the smaller the pump the greater the pull distance. That assumes a level weir and no leakage around the edges which isn't realistic. People wanting to spend a lot of money on a pond will pair a 4000 GPH pump with a 10" weir and it will indeed pull stuff into the skimmer so they assume a huge pump is needed, or is better. It isn't. But it's impressive to people impressed by excess which this hobby can certainly be about. Bottom line if you use a 500 GPH pump or bigger and a 10-12" weir you should be OK. And that single skimmer will clear the surface of even a 25x35' pond. Stuff may get hung up on sides, but no skimmer can deal with that. And on windy days stuff may blow away from the skimmer which again a bigger pump isn't going to solve. Really skimmer design generally has much more to do with the owner and how knowledgeable and/or if their goal is to have lots of equipment. If you make a skimmer the main thing to get right are getting the walls and floor where the weir is installed to be square and walls parallel so as the weir moves up and down there a minimal gap between the weir and wall. Messing that up then requires a larger pump to overcome the loss around the edges. The corrugated plastic makes getting the weir door perfect pretty each since it's so easy to cut. Trim the edges that move against the wall at 45 degrees instead of 90 degrees so the final trim is just a single layer of thin plastic.

Well people say all kinds of stuff on the internet - no filter is possible I suppose but if you have fish you really should have one - both to filter poop, debris, fish food, etc. out of the water.... AND to provide surface for your beneficial bacteria. If you havent already done so pls read up on biofilters and the nitrification cycle which changes ammonia (from fish poop/decomposing organic matter) to nitrite to nitrate. The first two are highly toxic to fish, nitrate is what your plants will need to live on. Look into external filters of some sort since your pond will be very small - if you want to diy there is a "mini-me" skippy filter, also other similar you can buy already made. Yes there are ways to have a water garden and/or a stream at the TOP of your waterfall be your filter - that actually would be a very effective more natural-looking way of doing it and maybe thats what you have in mind? The plants growing in and among your filter media would utilize the nitrate in the water from the fish - in that sense the plants and the other media (whether lava rock, bioballs or whatever) would be acting as your filtration . Re pump size - I'd get a slightly bigger pump , maybe 150 gph (because once you add in tubing to take it up to waterfall its going the flow will be lessened). You might even go higher gph depending on the height and length of the waterfall and the tubing (there are charts where you can look this up and figure it out.) Last but not least, no more than THREE GOLDFISH. Those tiny fish will grow to 6-10 inch long within a few yrs and 30-50 gallons per goldfish is the recommended minimum. Have heard that rosey red minnows are good for small ponds too - if you want more fish. They are short lived naturally unlike goldies which live 10-20 yrs under good conditions. No koi - instead you might want to go a pond store for goldies - there are some bred now for ponds which are beautiful with bright markings and long fins. Thats all I can think of - my first pond was about your size, so Im trying to think of what I wished Id known then. Im sorry to say I lost some goldfish at the beginning because some idiot at the garden center kept insisting I didnt need filtration, just let it "balance out" he said... meanwhile the pond kept getting muckier and muckier. Yes you do need some sort of filtration, whether a formal product you buy or make, or informal system of plants/rocks. Spoze it could work if you just net or vacuum out the debris and have some system of doing frequent water change, or of trickling water in and out. With that small a pond its doable, but I cant help but think if you have a pump, why not do the filter as well and make it easier on yourself.