IMO (in my opinion) you will hear all kinds of things from these dealers who want to sell you something. Algae is the most common problem we ponders have and unless there has been a miracle no one has come up with a concrete solution. I just bought a $1000 UV system from a "very reputable manufacturer" that doesn't work as advertised and when I tried to get advice they don't even return my phone calls or emails, so take it from there. Snake oil and deception are a common thing when you are getting options from those that have something for sale. Be very careful. You will find all kinds of chemicals and additives that people say solve the problem and maybe they do for them but each case is different so.............
If I sound cynical its because I am after being sold a bill of goods several times now. Of course I recognize that it is my fault for falling for it.

Here is a link that might be useful: My pond the way it was before the freeze.

You have said nothing about what kind of filtration system you use. A skimmer should be sized based on the square footage of your pond and not the number of gallons. Unless you have a skimmer/ filter combo, the main function or your skimmer is not to clear up algea as most of it is below the weir. Your filtraton system,(mechanical or plants)take care of that.
Water gardens are ok with a pump that circulates once ever two hours while a koi pond needs at least once an hour circulation.(a mag 50 would be too small for your pond as a koi pond.)
What was the reason you got for not using a bottom drain?

Our skimmer box has a filter and we have lilies, lots of water hyacinth, and water lettuce floating in the water, stream, and water box. BTW, I know lilies don't filter the water. Just mentioning we have them.

We weren't actually given a reason for not using a bottom drain. The dealers just said they don't recommend them.

Interesting on the pump not being big enough for the pond. When I posted on here asking for recommendations, that was the one recommended and the one recommended when we asked at several dealers, stressing we had koi.

I forgot to mention that we are also running gravity out of pool biological filter in addition to the regular pump. I'm not sure of the actual size of that one.

Thanks for your help.

To start with, check the discussion on this list for "Clear My Water". You'll find some good info there about clearing the water. Your equipment is probably fine.

Hi,
Algae is frustrating isn't it? The stuff grows on the bottom of arctic ice and in 180 degree water coming out of hot springs. If you have a pond, algae happens. IMO battling algae with chemicals, uv rays, and (to some extent) mechanical filtration is a war you can't win in the long run. Once you stop the chemicals, or the uv filter, or the mechanical filter clogs up the battle is lost.

My thoughts on reading your post are these:

First, patience. Your pond is new and needs time to find balance. Right now bacteria is establishing itself on the liner, the rocks, and every surface it can. This beneficial bacteria will convert the biological waste through the nitrate cycle-but it needs time to establish. Once the algae has less to feed on, the bloom will subside.

The purpose of the filter material in your waterfall filter and perhaps your skimmer is to give the bacteria more surface area to live on. 5,000 gallons going through a 22 inch waterfall filter probably means that the bacteria doesn't have time to convert the nitrates. Again, imo, I would divert half the water to an upflow biological filter and/or stream. 100 gallon per hour per inch of waterfall is plenty for a nice effect, that means yours needs about 2,200 gph. The rest of the water you could divert-gravel streams are beautiful and provide lots of surface area-stock tanks are ugly but do a great job if built as an upflow biological filter. Your equipment is fine. It's probably too late now to add a bottom drain and that is a pity. The ideal imo bottom drain and skimmer to settling tank, pump in tank to upflow biological filter, stream to waterfall, waterfall to veggie filter, weir to pond.

Your fish load is probably fine right now too. 4 large koi in a 6500 gallon pond is not unreasonable. The baby's aren't contributing much to the bio-load of the pond right now. Find homes for most of them before they get much bigger. Oh, and don't over feed them.

Algae happens. But thankfully so does balance. You can tip the scales in your favor by eliminating as much as the bio load as you can (skimmer for leaves-bottom drain for sinking mulm) increasing the surface area for aerobic bacteria, and keeping the bioload resonable for your pond size and filtration (mechanical, bio, and veggie.

But mostly try to be patient. Depending on water and air temps, at about 3 weeks from new pond start up you will have a BAD algae bloom; at about 5 weeks you will notice the water getting a bit clearer, between weeks 6 and 8 you will notice it getting markedly better. Next year it will happen quicker as the bacteria establishs.

Good Luck with your new pond! And patience!

Here is a link that might be useful: Come Join Pond Chat!

greenmountainponder has it pretty well down. Patience is the only thing that will work long term. For instance too many people drain their pond due to green water, if you do that you just start over you don't help anything. The cycle just starts over.
Filtration is more for fish in many water gardens, I would say with any fish I prefer moving the whole volume at least once an hour is better, but not necessary. A still pool will obviously get algae, but it is the minimizing of nutrients that algae feed on or true algae-cides that is a better control. pH is important, kh is a lesser known but equally important thing, but just having more plants to compete and starve the algae is best.
Ask a aquarium pharm. rep. and they will say chemicals are the bandaid and plants are the answer. Time, shade, and starving algae are what really help. Its not as fast as 'shocking' your pond with chemicals like a pool, but it will balance it out eventually.
We often use a natural treatment, AquaOne or some other bacterial treatment, early in the season, but larger or filtration plants will out compete nutrients for algae in the long run. UVs are the best answer if you want a quicker solution. Unless you have a properly fit UV system, you will have green water for the first year or two, and before you plants take off and shade.
If someone says they have a cure-all, they're selling not trying to help. Each pond is different and what works across the street may not work in your pond. Plants are the closest thing to a true cure-all. Good Luck.

If you know someone nearby who has a skippy or a freshwater tank then see if you can get them to rinse some of the sludge off the filter material into a large bucket(s). I found this to be the best thing. My bacteria level increased much quicker.

Of course you will want to make sure the fish in said pond are healthy so as not to bring in any parasites etc. But man....what a great way to start a pond!!

GMO

Ronda