Help Serious Algae Issue Causing Fish Deaths

Aquarist95

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Hello,
I have been keeping goldfish for several years now but I have never had such an issue as the one I am currently facing. I have too much string algae in my 2500 litre outdoor pond and it has recently caused issues with my fish getting stuck in it and swallowing it and having it stuck in their gills. I have had 4 fish deaths over the past 2 months because of this and I haven’t yet figured out what is going wrong. Water parameters are 0,0,<5. I am not overfeeding. I am doing water changes when necessary. It is not overstocked. Half the pond is in shade and it is only Spring weather here in Australia. I have many plants in the pond. I manually remove this stuff as much as I can but it is very hard. I use barley straw extract with minimal good effect to help and nothing works to control this stuff. I currently have the fish in a blow up pool temporarily as I have emptied the pond tonight in hope to get rid of as much algae as possible. I will be cleaning it tomorrow and refilling it. Any advice would be appreciated.
Thankyou.
 

allllien

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Hello,
I have been keeping goldfish for several years now but I have never had such an issue as the one I am currently facing. I have too much string algae in my 2500 litre outdoor pond and it has recently caused issues with my fish getting stuck in it and swallowing it and having it stuck in their gills. I have had 4 fish deaths over the past 2 months because of this and I haven’t yet figured out what is going wrong. Water parameters are 0,0,<5. I am not overfeeding. I am doing water changes when necessary. It is not overstocked. Half the pond is in shade and it is only Spring weather here in Australia. I have many plants in the pond. I manually remove this stuff as much as I can but it is very hard. I use barley straw extract with minimal good effect to help and nothing works to control this stuff. I currently have the fish in a blow up pool temporarily as I have emptied the pond tonight in hope to get rid of as much algae as possible. I will be cleaning it tomorrow and refilling it. Any advice would be appreciated.
Thankyou.
You could try adding ramshorn snails and just keep removing as much of the algae as you can by hand until it settles down. Maybe put up some shade cloth to keep the sun off it too.
 

Skavatar

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you said you had plants, what kind do you have? lilies and floating plants can help shade out algae.

barley straw helps to keep out floating algae in the water but does not really help with existing algae or algae that is growing on structure.

what type of filter do you have and what is the flow rate?
 

mjfromga

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I had bad string algae too earlier. My goldfish were getting stuck in it and everything as well. I stopped feeding them and changed more water and it cleared up pretty fast.

How many fish and how much do you feed? How deep is the pond?

I suspect over feeding or poor location (under trees) or questionable filtration, causing excess debris to build up in the pond that the algae is feeding off of.

DOC's won't show up on any standard water quality test but cause tons of harm in ponds, including excess algae, fish illness and death, low dissolved oxygen levels, etc.
 
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Aquarist95

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You could try adding ramshorn snails and just keep removing as much of the algae as you can by hand until it settles down. Maybe put up some shade cloth to keep the sun off it too.
I don’t know where to get these snails from but I will look into it. I do try to remove it but it’s hard to constantly get the net on and off to do so. I am also trying to set up some shade cloth but it is mostly in the shade already. Thankyou.
 
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Aquarist95

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you said you had plants, what kind do you have? lilies and floating plants can help shade out algae.

barley straw helps to keep out floating algae in the water but does not really help with existing algae or algae that is growing on structure.

what type of filter do you have and what is the flow rate?
I have 2 water lilies but they have been smothered by algae and now need to regrow. I also have many other plants such as umbrella grass, aquatic mint and others that I cannot remember the names of. I am planning on getting some water lettuce since summer is approaching and some frogbit and azolla. I have been using the barley straw extract but it doesn’t help much to even to prevent more from occurring. I have a large canister filter and 5000l pump
 
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Dave125g

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I don’t know where to get these snails from but I will look into it. I do try to remove it but it’s hard to constantly get the net on and off to do so. I am also trying to set up some shade cloth but it is mostly in the shade already. Thankyou.
I breed them in my 10 gallon. Ramshorns will eat any kind of algae. If you were stateside I'd send you a bunch. They multiply very quickly. My acaras eat them. Your goldfish may keep there population under control too.
 
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Aquarist95

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I had bad string algae too earlier. My goldfish were getting stuck in it and everything as well. I stopped feeding them and changed more water and it cleared up pretty fast.

How many fish and how much do you feed? How deep is the pond?

I suspect over feeding or poor location (under trees) or questionable filtration, causing excess debris to build up in the pond that the algae is feeding off of.

DOC's won't show up on any standard water quality test but cause tons of harm in ponds, including excess algae, fish illness and death, low dissolved oxygen levels, etc.
I haven’t been changing the water as regularly because my nitrates are never high but I guess something else is going on so I will be definitely increasing those water changes. There aren’t any trees but my pond is mostly in shade. My filtration is a very large canister and I have a 5000l per hour filter going. I will look into the DOC’s.
 

mjfromga

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Ramshorn snails won't eat string algae. I don't think plecos will either. They might. In either case, it makes little sense to add living things to a pond already suffering deaths and is clearly not stable. In addition, a 30 day quarantine should be done on new fish... So buying any fish and just "throwing them in" definitely is not advised and might cause more issues than help.
 

Dave125g

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Ramshorn snails won't eat string algae. I don't think plecos will either. They might. In either case, it makes little sense to add living things to a pond already suffering deaths and is clearly not stable. In addition, a 30 day quarantine should be done on new fish... So buying any fish and just "throwing them in" definitely is not advised and might cause more issues than help.
My Ramshorns do.
 

maggie thecat

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You may be getting fertilizer runoff from the surrounding landscape. Besides manually removing the algae, upping aeration, using barley extract in conjunction with monthly additions of mulm digesting beneficial bacteria and adding more plants, especially oxegenators like anacharis can help. In a worst case scenario, hydrogen peroxide (3% peroxide 16 ounces per 1000 gallons) or a commercial algaecide formulated for ponds, used as directed may provide relief.
 

allllien

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Ramshorn snails won't eat string algae. I don't think plecos will either. They might. In either case, it makes little sense to add living things to a pond already suffering deaths and is clearly not stable. In addition, a 30 day quarantine should be done on new fish... So buying any fish and just "throwing them in" definitely is not advised and might cause more issues than help.
Mine eat string algae -I once added a rock with string algae to one of my tanks with snails because I liked the look of it, well the snails ate it all and left me with a plain old boring rock lol. So I know they eat it. I don't think she said the water was unstable, rather the fish were dying from getting tangled in the algae.
 
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