Sludge!

[Janne]

I've been pond keeping since 2005 and in my current location since 2018. My pond is 5' x 20' with a bog and average depth of 3.5' (4' at the deepest end at the spillway). The volume is about 4000 gallons, including the bog. This season has been brutal, perhaps because of the heat, exacerbating the effects of the concrete inferno (backyard). Since late June, it has been necessary to change the filters in the skimmer at least twice a day. I added a homemade filter box at the spillway, put sludge reducers in the pond, monitored water quality daily. KH and pH values were initially a problem. Current readings (pH-8.0, KH-180, NO2-0, NO3-200, NH-0) have been consistent for at least 6 weeks. Filters still have to be cleaned/changed twice daily. IS THIS BECAUSE OF FISH LOAD? There is a lot a algae.

In the pond there are currently 14 koi that I have had since 2005 or so. They now average 12"-18" in length. (One big guy, Lazarus, appears to have a girth of about 16"!) I have managed to rehome six 7" goldfish (offspring from a spawn 2 years ago). The current population appears to be healthy. There are also 1 comet and 4 goldfish that remain, as well as 7 baby koi (each has barbells). (I've tried to catch two more goldfish, but they have been ellusive!!). My husband is fascinated with the little koi and resistant to their removal. Only one has ventured out of the bog area, but upon encountering a big fish, it made a rapid retreat. The big fish cannot get into the bog.

I am quite tired of cleaning filters everyday. Not wanting to add to the amount of plastic waste, I rinse them. The waste water goes for watering ornaments plants and, since I am wary of putting it on vegetables. This requires "hauling" buckets of waste water to thirsty plants.

Suggestions of how to fix my sludge issues would be appreciated!

 

[Mgessert]

Yes, I would say that your koi are outgrowing the pond. So pretty though!

 

[Janne]

Thank you Sarah. I do appreciate your taking time to share your thought.

 

[JRS]

Not sure of the best answer but a few thoughts.

Seems like your nitrate is very high for a pond with a bog. Assuming this is also contributing to the algae issue. Is the sludge in your skimmer greenish? Thinking of water column suspended algae. How big is your bog?

Any fresh water being added besides topping off for evaporation? Lack of fresh water can contribute to nitrate concentration and then algae.

Fish load is responsible for most of the issues we have in our ponds. You have a lot of big fish, more food= more waste= more cleaning.
You are on the right track reducing population. Can you reduce feeding also? Hard when they come begging. Perhaps if your husband had to help clean the filters, he might be less resistant to population reduction?

 

[Lisak1]

The simple answer is yes - you have too many fish. And the addition of seven more koi, as they grow, will only make things worse. When it comes to overstocked ponds, one of two things will happen, and both will end the same way - with fewer fish. Either you remove them, or Mother Nature will. Anyone who has watched fish die due to poor water quality will tell you it's terrible. Maybe if your husband understood it's not just a housekeeping issue - it's a matter of life and death for those fish. I do think you're overestimating the size of your pond, based on the numbers you gave us - I would figure it to be under 3000 gallons. In any case, 14 koi is a lot for most garden ponds.

Getting more plants growing in the pond would help, but your pond looks more modern in design, so that might be difficult if there are no shelves or rocks to tuck plants into. The best, more forward thinking, and with the best possible outcome for all of you is to start rehoming the big fish. If your husband enjoys watching the little ones grow, that's fine, as long as he's prepared to get rid of them as we when they start to outgrow the pond.

 

[Janne]

The sludge in the skimmer filters is dark brown. The skimmer basket at least a handful of algae. Some of the gravel and rocks in the the bog have a covering of brownish green sludge. The bog is 3' x 5', with pea gravel to a depth of about 3 feet deep.

The nitrate level has never been this high. I was told (obviously falsely) that as long as the nitrite level was 0 there was no worry about the nitrates. I did about a 10% water change earlier in the spring. I need to check the nitrate level in the city water.

I have reduced the amount of food that the big fish get, and no longer have husband feeding them.

Thank you for your thoughts! Much appreciated!

 

[Janne]

The simple answer is yes - you have too many fish. And the addition of seven more koi, as they grow, will only make things worse. When it comes to overstocked ponds, one of two things will happen, and both will end the same way - with fewer fish. Either you remove them, or Mother Nature will. Anyone who has watched fish die due to poor water quality will tell you it's terrible. Maybe if your husband understood it's not just a housekeeping issue - it's a matter of life and death for those fish. I do think you're overestimating the size of your pond, based on the numbers you gave us - I would figure it to be under 3000 gallons. In any case, 14 koi is a lot for most garden ponds.

Getting more plants growing in the pond would help, but your pond looks more modern in design, so that might be difficult if there are no shelves or rocks to tuck plants into. The best, more forward thinking, and with the best possible outcome for all of you is to start rehoming the big fish. If your husband enjoys watching the little ones grow, that's fine, as long as he's prepared to get rid of them as we when they start to outgrow the pond.

Thank you! My arithmetic skills strike again. (I can do higher mathematics, but arithmetic has always been a challenge, even worse as a approach 8 decades.) I do/did have a few plants. This year, the water lilies did not thrive. The papyrus and canna were not going well either. I suspect that the water quality had something to do with that. This is the first year that my plants have done poorly.

I'm wondering if a more efficient filtration and purification system will allow us to keep the "bubbies" that we have had for 17 years, since they were three or four inches.

Again, thank you for your response.

 

[Mgessert]

Well, in my experience, stopping the husband feeding them will definitely help.

 

[Janne]

Thank you. I agree. Also getting him to clean the filters twice a day would be helpful!

 

[Lisak1]

I didn't use math (not my strong suit either!) - there are pond size calculators on the internet that make it very easy to estimate. And formal ponds are far easier to calculate than an irregular garden pond. Knowing how many gallons your pond is (or at least a very close estimate) can be critical.

Water lilies aren't much help for filtering a pond. Floating plants, irises and rushes, watercress - anything with big fast growing root systems. And the best results come from anything that has its roots directly in the water. I doubt it was water quality though - plants thrive in pond water that's full of nutrients. Maybe something else going on there.

NO POND should need filters cleaned twice a day. That's just unsustainable. And yes, you CAN bump up the filtration on a pond and overstock, but eventually your pond will reach a point where it can no longer support the size and number of fish. That's the "tipping point" - it happens fast and generally without much warning. Every pond has a limit, no matter how large. You really don't want to find out what that is.

Here's a helpful chart that explains the difference between koi and goldfish - check out the waste production difference between 4-4 inch goldfish and one 16 inch koi. It's enlightening! And by "waste" they don't use mean poop, although that's part of it - fish "breathe" in the water and expel waste that way, too. That waste isn't filtered by mechanical filtration - that's where the biological filtration comes into play.

Here's the chart:

Koi Length and Weight - Ammonia Produced, and Waste Produced

This chart also lists koi weight by weight and how much ammonia and waste they produce. Koi get heavier as they grow and produce more ammonia and waste.

russellwatergardens.com

 

[Souper09]

I’m on the too many fish side of your problem, a most difficult solution is to remove some fish. Its painful to remove if you don‘t have someone to adopt them. If you’re cleaning filters every day sludge removal won’t work.

 

[rubyduby]

I didn't use math (not my strong suit either!) - there are pond size calculators on the internet that make it very easy to estimate. And formal ponds are far easier to calculate than an irregular garden pond. Knowing how many gallons your pond is (or at least a very close estimate) can be critical.

Water lilies aren't much help for filtering a pond. Floating plants, irises and rushes, watercress - anything with big fast growing root systems. And the best results come from anything that has its roots directly in the water. I doubt it was water quality though - plants thrive in pond water that's full of nutrients. Maybe something else going on there.

NO POND should need filters cleaned twice a day. That's just unsustainable. And yes, you CAN bump up the filtration on a pond and overstock, but eventually your pond will reach a point where it can no longer support the size and number of fish. That's the "tipping point" - it happens fast and generally without much warning. Every pond has a limit, no matter how large. You really don't want to find out what that is.

Here's a helpful chart that explains the difference between koi and goldfish - check out the waste production difference between 4-4 inch goldfish and one 16 inch koi. It's enlightening! And by "waste" they don't use mean poop, although that's part of it - fish "breathe" in the water and expel waste that way, too. That waste isn't filtered by mechanical filtration - that's where the biological filtration comes into play.

Here's the chart:

Koi Length and Weight - Ammonia Produced, and Waste Produced

This chart also lists koi weight by weight and how much ammonia and waste they produce. Koi get heavier as they grow and produce more ammonia and waste.

russellwatergardens.com

This is wonderful information that Lisak1 has given you...Another good source of information is:
koiphen.com since your focus seems to be more on keeping a lot of big koi in a small containment than a garden pond...Some of the professional koi breeders do overstock but their filtration is super efficient...No one that I know cleans their skimmer filter that much...I only clean mine once a week here in Florida which has a very high heat index...I also do not have any algae growing besides the good carpet algae...BUT, I only have shubunkin goldfish which are very pretty with a lot of personality and much less waste....Good luck and keep us posted!

 

[Janne]

I didn't use math (not my strong suit either!) - there are pond size calculators on the internet that make it very easy to estimate. And formal ponds are far easier to calculate than an irregular garden pond. Knowing how many gallons your pond is (or at least a very close estimate) can be critical.

Water lilies aren't much help for filtering a pond. Floating plants, irises and rushes, watercress - anything with big fast growing root systems. And the best results come from anything that has its roots directly in the water. I doubt it was water quality though - plants thrive in pond water that's full of nutrients. Maybe something else going on there.

NO POND should need filters cleaned twice a day. That's just unsustainable. And yes, you CAN bump up the filtration on a pond and overstock, but eventually your pond will reach a point where it can no longer support the size and number of fish. That's the "tipping point" - it happens fast and generally without much warning. Every pond has a limit, no matter how large. You really don't want to find out what that is.

Here's a helpful chart that explains the difference between koi and goldfish - check out the waste production difference between 4-4 inch goldfish and one 16 inch koi. It's enlightening! And by "waste" they don't use mean poop, although that's part of it - fish "breathe" in the water and expel waste that way, too. That waste isn't filtered by mechanical filtration - that's where the biological filtration comes into play.

Here's the chart:

Koi Length and Weight - Ammonia Produced, and Waste Produced

This chart also lists koi weight by weight and how much ammonia and waste they produce. Koi get heavier as they grow and produce more ammonia and waste.

russellwatergardens.com

Thank you for the reference.

 

[Janne]

This is wonderful information that Lisak1 has given you...Another good source of information is:
koiphen.com since your focus seems to be more on keeping a lot of big koi in a small containment than a garden pond...Some of the professional koi breeders do overstock but their filtration is super efficient...No one that I know cleans their skimmer filter that much...I only clean mine once a week here in Florida which has a very high heat index...I also do not have any algae growing besides the good carpet algae...BUT, I only have shubunkin goldfish which are very pretty with a lot of personality and much less waste....Good luck and keep us posted!

In the past, I never had to clean filters daily (sometimes twice daily). It will be difficult to part with the koi since we've had them for so long. Thank you for your response.

 

[Lisak1]

It will be difficult to part with the koi since we've had them for so long.

I think we all understand how you feel - we just "watched" @Tula part with her koi and share how emotional that experience can be. But if you truly love your fish - and I believe you do - then you want what's best for them. And the saddest part is, if we don't address these issues ourselves, Mother Nature will take care of it for us - and she is a cruel master. I only wish people who sold koi were more responsible and informative so ponders weren't constantly finding themselves in this situation.

Those of us with low maintenance ponds know how rewarding this hobby can be, and it is always worrisome when someone is spending far too much time on the "not so fun" aspects of ponding, because that leads to a desire to just give it up. Your pond should be relaxing and enjoyable and worry free 90% of the time. Reducing your fish load will get you there.