How To Clear A Green Koi Pond in 2-1/2 Weeks

By mike | Product Reviews

May 07

First I want to say I am not an Amazon Affiliate, not am I affiliated with any of these two products I mention. I posted this just to help other newbie Koi Pond owners like myself.

13 Months ago I moved back to Carver, Massachusetts. The house I bought came with a KOI Pond that wasn’t cared for very well by the previous owner. The woman I bought the house from was a middle aged Nurse who lived alone and worked a lot. Her son helped her the most he could, but she had inherited the fish pond 3 years earlier when she bought the house. Legend had it that there was 4 fish living down there, but it was so green I couldn’t see anything.

Koi Pond last year

This is what it looked like last year, when I first bought the house

My son in law bought a bucket of shiners and threw them in there as well about a year ago.

Anyway, I knew nothing about KOI Ponds, and thanks to Reddit I was able to learn from 3 different sub Reddits. If you have a Koi Pond, I highly recommend subscribing to these:

3 SubReddits:

After reading about Koi Ponds online and on Reddit, I learned the first thing I had to learn was how many gallons my pond was. I found this Pond Volume Calculator online, but my pond has an odd shape and different depth levels so the math became complicated. So I decided to drain my pond. I bought a sump pump and as soon as a turned it on I timed the pump filling up a 5 gallon bucket. Then I timed how long it took to drain the pond and I did the simple math.

I found the 4 fish and I put them in a 5 gallon bucket and I kept about 200 gallons in the pond so the shiners would survive. I then cleared out a bunch of nasty muck on the bottom.

Koi Pond Muck

I filled up this trailer 3 times with the muck that was on the bottom of the pond.

I’m kind of in the middle of the woods, so lots of debris falls into the pond. Here is a photo from Google Maps that shows where the pond is:

Aerial view of Koi Pond

Lots of leave fall into the pond and pine needles.

So it was May of 2015 when I bought this house. After I drained it for the first time, it was pretty much green by the time I filled it up again.

I don’t like to use any chemicals, and I drained this pond at least 3 times last year. That’s when I started researching on Reddit, and I even visited my local KOI Pond supplier. They had a UV system for $800.00, and there’s no way I was going to spend that kind of money.

So, the winter came.

Snow covered Koi Pond

I had Christmas lights and it looked cool when it was covered in snow at night time.

Aerotor keeps Koi Pond from freezing

During the winter I kept the water fall and the aerator running so the pond wouldn’t completely freeze, and to ensure the fish had plenty of oxygen. I had read that fish don’t need much oxygen during the cold months, but I didn’t want to take any chances.

So once the spring of 2016 came back, I had a lot of work to do, although this frog didn’t seem to mind the pea soup water:

Frog in a koi pond

So this spring, I purchased 3 items from that made a huge difference:

  1. Jebao 36W Aquarium Koi Fish Pond UV Light Sterilizer : $91.99 Shipped (LinkUV system for Koi Pond from Amazon

  2. Two EasyPro BB05 Bio-Balls Filter Media for Ponds: $80.57 Shipped (LinkBio Balls Koi Pond Filter


UV Pond Clarifier System (Not to be confused with UV Filter):

This product had a 4 star rating on Amazon, and here are some of the positive reviews:

Let me start by saying this thing is the bomb! I had a little trouble at first connecting the tubing to the connectors. I emailed the supplier and explained the issue I was having. They got back to me very quickly and advised me to put the plastics pond hose in some hot water to make it a little more playable. Well I tried that and still had a little trouble. So what I did was put it in hot water and stuck the end on to the end of my shop vac attachment. (The attachment I used was the cone shape one to get in tight spots. It starts out small and keeps getting larger in diameter) Let me just say that worked GREAT! Put a inch or two of the pond hose in hot water for about 20 secs and then stick the shop vac cone in it. It helped stretch it out perfectly. Anyway, I got it all attached and turned it on. I have a 9-10,000 gal pond. With in a couple days I could see improvement. (My pond was green as a gourd) I have had this pond for 3 years now and have never been able to keep it clean and clear. Well its been 3 weeks and I am able to see almost to the bottom of the deep end. My pond is a 18×36 shallow end is 2 1/2 feet deep and the deep end is around 6 or 7 feet deep. For the size pond I have I should probably use two of these UV lights. How ever, we have a crane problem so I really didn’t want it to clear. But to late now. The pond looks beautiful and I enjoy seeing my koi. So if your asking your self does this thing work? The answer is a big fat YES! I will be buying another one of these as a back up or maybe just dig another pond! If your wondering what size pump I’m using it was the 250.00 one from Lowes. Its a couple years old now so I couldn’t tell youths gph. Once again I don’t know how I ever lived without this thing. Plus…. this is my first ever review of anything I have ever purchased on amazon so I hope I’m doing this right. I wish I could share the before and after pictures of my pond. You wouldn’t believe it, I didn’t. You won’t be disappoint specially if your pond is smaller then mine.

GREAT product, GREAT customer service. had problem with one bulb But they quickly responded and replaced it. no need to send the other bulb back. hassle free, the uv light sterilizer is working Great, my Pond is WOW ! ! never been so Clear. so nice to speak to them on the phone. Highly recommend this product the price is super..

There were some bad reviews, but I learned a long time ago that usually people who are mad leave reviews. I did filter out some good ones, so I figured for less than $100.00 it’s worth the risk. There were a few answers on the Amazon page that were answered incorrectly, including this one:

Is a UV clarifier submersible

It is not submersible! That first person who answered should remove his/her answer. I contacted them through Amazon and suggested they take it down and they still haven’t. The problem is, before the question only shows his/her answer on the product page. I had to click to see the other two answers. Some people may ruin their device by listening to this one person.

So when I received the UV system, it was very easy to install. I put it between my pump and the waterfall.

UV Clarifier installed

You can spin the ends to accomodate the direction of the hoses. They say you can also mount it vertical if you want.

Here are the tips I added to my Amazon review:

1) The bulb has to be installed, it’s best to do it first. Mine didn’t appear to seat tightly but it works.

2) The unit is not submersible!

3) When hooking up your existing hose to the UV unit, have a pan of hot water with you. Dip the end of your hose in the hot water for at least 30 seconds. It will allow it to easily expand a little to make this task easy.

4) There is an indicator window that glows blue to verify the UV light is working. It’s hard to see when it’s daylight, but at night you will see the blueish glow clearly.

The BIO Balls:

This product has a 4-1/2 star rating on Amazon, and some great reviews:


Why, why, why didn’t we know about these balls sooner? They are lightweight and work so much better cleaning the water in our waterfall. We have a 55 foot stream that dumps into a 10x12x1 foot pond and these balls keep the water clear and beautiful. My dad told us to get lava rock, which is heavy, messy, and hard to clean. I am so glad we found these balls and used them instead!

They filter. They’re in a bag. They work as described. I have a submerged in a pond that I use these with. I seem to get a lot of debris and dirt because of the fish and the trees around the pond. I use a mesh bag around the pump which I then insert into the bag these balls come with and fill the gap with the bio balls. I used to have to clean the pump and bag every few days and now I can go weeks!

I don’t usually write reviews of products…But this time I feel obligated to. I am simply amazed by how fast these bio balls cleared out my pond. From mucky water, not being able to see the fish, let alone the bottom of a 4 foot deep pond, to crystal clear water in 24 hours! I used 960 of these balls total. Absolutely amazing! These are very sturdy balls, look like they will last a lifetime.

These things worked out great. I had lava rocks in there before. These are super easy to clean. It’s basically a bunch of plastic textured balls that sit in a mesh bag and floats. I bought two.

I just cleaned these 2 days ago, and look at what it filtered already:

Bio balls for Koi Pond Waterfall

They float on top of the water

Koi Pond Filter

Here is a closer look. In just two days a lot of gunk has accumulated. It cleans very easy

So after 2 1/2 weeks, here it is:

before & after photo UV Koi Pond


So I still have some skimming to do but my fish have been very happy. All four of them survived. There is still one shiner and a few babies that are hard to find. It’s so relaxing sitting by the pond, hearing the waterfall. I never would of built a KOI Pond, but I’m glad my house came with one. It forced me into it.

I don’t have any pets, but my yard is full of deer, wild turkeys and all kinds of birds. The KOI Pond complements all of the other nature around me.

Again, please note I AM NOT an Amazon affiliate, I just buy a lot of stuff from them because it’s inexpensive and reliable. This is not an advertisement, it’s just simply my review.


    About the Author

    I've been working in digital marketing since 1994. I'm the original founder of Showroom Logic based out of Miami Florida. I moved back to Carver Massachusetts to be closer to my family. After my second winter back, I am questioning my sanity.

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