I have a small fish pool that’s being overtaken by algae. The pond is about 250 gallons, and is home to twelve goldfish and two water lilies. There’s a large pump and fountain that filters and aerates the water.
I want to cut down the amount of algae in the pond. I’ve used anti-algae chemicals in the past, but I’d prefer not to use them again. I’ve tried to pull out clumps of algae, but it’s slimy, smelly and difficult to handle. This time, I’d like to use a more biological solution: fish that eat algae.
Does anyone have recommendations on what species and number of fish could work?
If you feed the fish in your pond with some sort of commercially available food, you should stop. They will fend for themselves quite well and you will avoid having the uneaten food and additional excrement become fertilizer for algae, which is a plant.
Also, try some more plants that will compete with the algae for light and nutrients.
As far as fish go, I can’t recommend any outdoor algae gobblers, but the Plecostomus genus of catfish will clean an aquarium of algae real quick.
I use hornwort in my pools.
It begins growing in the Spring, there is a period of green water and soon the hornwort out competes the algae for nutrients.
If you can’t find any, I regularly throw it away and would be happy to mail a bunch to you for postage.
I’m assuming from your humorous location that you’re in southern California. A plecostomus should be OK at the temperatures and conditions you’re likely to have. Like goldfish, they have the potential to get really big if the conditions permit it - I’ve had mine get 8-9 inches in a small tank, and I’ve been told they’ll get up over 18 inches given the opportunity.
Of course, even goldfish will eat some algae if they have less food available.
When it comes to food, remember that dietary needs change a lot with the water temperature. What is just enough food during the summer is way too much in the winter. In fact, many people with outdoor koi or goldfish ponds simply stop feeding altogether from Dec-Feb. (And this was true even on the central coast of CA, not just where it gets really cold in the winter).
The industrial solution to this problem is overkill, but would involve diverting some of the water before it gets to the pump so that it runs through UV sanitizers. This will kill any algae floating free in the water without any poisons or water additives. That doesn’t kill existing mats of algae, but it will stop them from forming.
I’m in Zone 7, and have a light fish load. I usually don’t feed them at all. I believe you are supposed to stop feeding goldfish when the temperature reaches 50.
The coldest it normally gets where I’m at is about mid 40s at night, low 60s during the day. Hottest normal is mid 90s day, mid 70s night. The pool gets full (SoCal) sun from mid morning to mid afternoon.
The goldfish are six to eight inches long. I feed them goldfish flakes once a day. I’ll ween them off and see if they make a dent on the algae. I didn’t realize goldfish could eat algae. :smack: (The pool and everything in it came with the house, so I don’t know much about fish care. I feed them because that’s what I though they needed.)
The hornwort is interesting, but it looks like I’d be merely replacing my runaway algae with runaway hornwort. The lilies cover about three-quarters of the pond surface when they’re at their max, but the cool has made them dormant. Algae were not a problem during last summer.
The plecostomus may be what I’m looking for. Would one be enough? Would two starve?
Snails. Apple snails especially. Or Amano shrimp - they are great fun to watch. Another possibility is to just grab some pretty guppies at the beginning of each Spring season. they only live about a year, and the cold temps should slow them down enough to keep them from over taking the pond. guppies are the best algae eaters I’ve ever had. . .
It doesn’t use harsh nasty non-environmenntally safe chemicals. There’s this new type of fish available that all the conservationist types are all excited about. It just eats algea, not your little fishes. So you can put it in your pond and it will happily clean it up of all the agea. I think its called “asian carp” or something.
I’m sure if you do a google search you can find out about it.
Apple snails are a very damaging species in some areas and illegal to own in some states. They are considered an invasive species and are a very bad pest in rice fields.
If possible get rid of the goldfish. Goldfish stir up the bottom of your pond mixing in nutrients that cause algae growth. Tillapia are a good substitute. Also try to have at least 50% of the surface of your pond covered with lillypads or floating plants. If you have a liner another thing to do is put all your plants in special pots for waterplants. You won’t have soil over the entire bottom of the pond so less soil will get mixed in.
Goldfish, being glorified decorative carp, eat just about everything, and will dig around in gravel to get to it.
That said, their mouth parts aren’t as good as getting algae as something like a pleco, but they will eat the algae once it gets thick enough.
I would get at least two. They’ll eat goldfish food too, if the algae gets too thin (and if the goldfish let any of it get to the bottom).
That said… the other posters are smart to take environmental concerns into account. I have no idea if plecos represent a threat. Mine just stay put in the tank.
The bottom line is that the end product of the fishes’ metabolic process is going to be plant food. You have to deal with it in some way. If you set up a trickle system to replace the water on a continuous basis, that can cut your algae. If you put other plants into the system to compete with the algae for plant food, that can help. Adding other fish and snails is more likely to increase the biological load, so it won’t really help. They won’t be removing the algae from the system, they’ll simply be converting it into more metabolic end product. Reduce the biological load–feed your fish rarely, only as a supplement, if at all–and either dilute the end product with fresh water, or increase the plant metabolism to utilize more of it.
But they are beautiful. I saw a large one, born in the pool and red unlike the tank raised ones, jump a foot into the air. It looked like a flame bursting from the pool.
Any fish that jumps out of the pool will land in my yard and become food to the local cats or coyotes. There’s no chance for escapees.
That’s an interesting way of looking at it. The system loses water due to splashing from the fountain, which I replace on the weekends. I’ll definitely do the elimination of fish food.
Yes. There’s no way I’m removing the goldfish. They are a beautiful deep orange color, and several have interesting white patches.
I certainly can understand wanting to keep the goldfish. If they are important to your enjoyment of the pond you should keep them. My suggestion was for someone to whom the fish were just an incidental part of the pond. Good luck with your pond.
