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- Feb 15, 2018
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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.
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.
