Algae in inherited pond, suggestions appreciated


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My wife and I bought our house 2 years ago (PA near the MD border), and it came with an ~4500 gallon koi pond that we have struggled with two summers now. With the 3rd summer looming, we'd like to improve this.

Our main problem is algae, the water is always green to the point you can only see the fish when they come up to the surface. We don't get mats or strings per se. It does seem to stringify, but if you touch it it disintegrates. During the coldest of the cold weather, the water is clear, and the algae settles to the bottom and surfaces, but with water action it stirs up and clouds visibility. The pond gets full sun for a majority of the day. I did a silly drawing to describe what we are working with.



The water tests as of a few days ago gave me this:

PH: ~7.25
Ammonia: < .25 ppm
nitrite: 0 ppm
Phosphate: 5 ppm

This is a rubber lined pond. There is a random plant I can't identify in the water by the mouth of the stream, and a large area of cattail reeds across from it. We have several water lilies in pots. And I usually put water lettuce at the head of the stream, and the stream flows through this, providing a really mucky environment by the end of summer. Two pumps circulate water: a 2500 gph pump that splits to supply a gentle "stream" and a waterfall. I can control the level of the split by turning a directional valve. The waterfall tub is just a plastic oval style. It has like 3 inch PVC pipe pieces with holes layered on the bottom, with mesh bags of lava rocks on top, and water comes from the bottom and rises to fall over the lip. The line to the split comes from the pump which is accessible, but it goes under the cattails bed, so I can't access much of it. The 2nd pump is a 1200 gph that flows thru a 57 watt UV sterilizer. The outlet from that gives me a rotational swirl in the water, and I leave that spaying year round to help keep the water from freezing in winter and to tell me that it is indeed going through the UV all the time. I have 2 air bubblers in the deepest part of the pond.

Fish: various koi I haven't identified. We started with 27 large monsters (think 14" to 20"). Thinking we had too many fish for the size of the pond, we downsized to roughly 10, but they bred this past summer and we have about a dozen 6-inchers in there too, now. We feed them pond fish food pellets (Purina Game Fish Chow), one a day in early spring and late fall, and twice a day during the summer. We stop feeding in the October time-frame, and probably don't start back up until late March. Each feeding consists of about 1/3 to 1/2 cup of pellets strewn wide across the pond to give the little fry a chance. The fish do attack the roots of the lilies and the cattails area. A couple fry died over this winter, a first. I am largely guessing the amount of food to provide. It takes about a minute, or two max to locate random pellets, for them to eat it all at each meal. Trying to not overfeed them as I thought it could be contributing to my issue as well.

In the spring we empty the pond, scrub it down, hose the lava rocks, and replace the water. Generally we don't do anything with water the rest of the year. There is 0 chance of runoff into the pond as it is raised from the surrounding ground. It can only get water if we manually add, which we do in the heat of the summer, or from rain. It has a low spot to automatically drain if it gets too high.

We added the lilys for shade for the water and to hopefully help balance the water levels (which is also the reason for the water lettuce). I upgraded to the 57 watt UV sterilizer from a 25 watt, and went up to the 1200 gph pump to increase flow through it. We've tried algae killer chemicals. We've tried treating it with beneficial bacteria. I use muck tablets regularly. Nothing has really provided any relief from the algae.

So I am soliciting for suggestions. My thoughts have included, among others, adding snails. At some point I'd heard that the lava rock has a limited lifespan for harboring bacteria, and was considering bio-balls to replace them. I was wondering about adding additional levels of filtration mats in the waterfall tub. I'd like to add a pond skimmer but given the construction and electrical supply I'd have a hard time working it into the design.

Anything is appreciated.
 

Jhn

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I see numerous issues contributing to the green water. Here are a few ways to solve it.

Increase flow in pond, you need 1.5-2x volume per hour. For a 4500 gallon you would want 6800-9000gph in turnover.

Secondly , Some like the uv clarifier, I don't. As it is only trying to solve a symptom green algae and not the problem, excess nutrients. It can actually contribute to the problem as it is just killing the algae cells as it passes the uv light them dumps them back into the pond.

Don't dump chemicals in the pond , it kills the algae, but then the algae just dies in the pond dumping all the nutrients it absorbed back into the pond to start the cycle all over. Same as clarifier treating the symptom not the cause.

Cut back on feeding they will find stuff to eat in the pond. They don't really need to be fed twice a day, to me once a day is fine as long as they are consuming all the food 5 minutes or so. I feed my fish few times a week even in the summer.

You are still overstocked abit with 10 14-20" koi, keeping in mind they get much bigger than this and as you found out reproduce.

Stop emptying and scrubbing your pond every spring. You basically are ridding your entire pond of the biofilm it developed and are essentially starting over. You are better off waiting until the weather warms some and cleaning out the bottom of the pond witha net and/or pond vac. Don't empty it to do this.

Make sure you have plenty of plants to out compete the algae for nutrients and essentially starve it out. One way to do this is turning your waterfall tub (depends on size of tub) into a bog, addy1 has a stickied thread in the pond construction section on how to build this. Or even add a larger tub/stock tank to do this.

You can beat the green algae, just takes getting your pond in balance and healthy. Once done it will be a lot less maintenance on your part.
 
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I agree with Jhn, a lot of fish, not enough circulation.
I'm not seeing a filter mentioned that will trap suspended detritus that can then be removed from the pond.
Bioballs are better than lava rocks because bioballs can self clean with sufficient water circulation while lava rock will clog up and release nutrients back into the water column. The present plant density is not sufficient to absorb the nutrients being produced by the fish and feeding schedule.
Have you measured the KH? It's one of the most important values to keep track of.
PH can fluctuate during the day so what time you took the PH reading is important.
 
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Welcome to the GPF!

I'm just going to agree with what they said up there - they covered all the high points!

We'd love to see pictures of your pond!
 

brokensword

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@Jhn ; isn't the phosphorus reading a bit high? Algae likes phosphorus, no?

And of course, more plants would help this reading, too.
 

Jhn

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@Jhn ; isn't the phosphorus reading a bit high? Algae likes phosphorus, no?

And of course, more plants would help this reading, too.
I agree it is, reduced feeding as fish food contains phosphorus and especially as you mentioned adding more plants will help in lowering the reading. Just didn't mention it specifically as getting the pond in a healthy balance should address the issue.
 

addy1

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Welcome to our group! All good suggestions up there.
 
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When was the last time you changed your UV lamp?
 
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Thank you all for the replies! (I was expecting an email notification otherwise I'd have gotten back sooner.) I'd gotten several suggestions in the past but they all conflicted with one another, chemicals vs no chemicals and such. I'll parse through all these and see what we can do.

To address some of the questions I saw:

"Have you measured the KH?" No, I'm not aware of that one. My test kit only had what I listed above.

"PH can fluctuate during the day so what time you took the PH reading is important." It was mid-afternoon on a cold day.

"isn't the phosphorus reading a bit high?" Yeah, it is, and this was in line with my expectations and what research I had done.

"last time you changed your UV lamp?" - the bulb is under 1 year at this point


Thanks!
 

Becky

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(I was expecting an email notification otherwise I'd have gotten back sooner.)
There is a way to get email notifications when someone replies to your topic - click on 'Watch Thread' at the top of the page, and then select email notifications (y)
 
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Welcome to the forum @Mike Durakovich , have you had any luck in the last couple of weeks with your algae problem?
So we haven't actually done anything yet. This coming weekend we are going to drain the pond completely. The fish will be re-homed temporarily for the summer. I probably failed to mention that while this is a rubber lined pond, it is bare liner, there are no rocks in it at all, except for for the couple the fish pick out of the lily buckets.

We are going to systematically remove the entire thing down to bare dirt, reshape it to be less rectangular, add in a large skimmer box, upsize the pump to the waterfall, totally redo the waterfall so we have a multi-level drop stream as well as a direct spill into the main area, get rid of the slope and tier that half, and, and, and...

We hope to have a much more attractive feature that is better able to maintain the right balances for easy maintenance, ultimately. I'll document along the way. And thanks to all for the advice.
 

Mmathis

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I have to admit that I am joining this conversation late, and I haven’t gone back to read everything — but I get the gist of what’s going on. I have to say that I admire your dedication to this project! You have a huge project ahead, but I think you are going to get a lot of enjoyment/pleasure/satisfaction out of the process, as well as the end result! There’s just something special about designing and building your own pond. I think it gives the pond owner a different perspective, and possibly a greater appreciation for the hobby.

Yes, keep us posted! Pictures, lots of pictures! It’s going to look great! And best wishes!
 

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