Question
(I live in San Jose,California.)Is there such thing as algae-controlling fish? My pond is about 200 gal. and algae is covering everything. Most of them are on rocks and plants.
Also, one afternoon I came home to find half the water gone (due to a leak) and only 5 carps & mosquito fish out of 15 alive. I also found the back half of a fish. Do you have any possible suggestions of what happened to the fish and how I can prevent it?


Answer
I'm sorry about your pond troubles.  It sounds like you had a predator attack.  It may have been a heron but they normally swallow fish whole and would have eaten all the fish. Perhaps it was a cat or whatever kinds of native predators you have around San Jose.  Around here in MD, it's usually raccoons.  Do you have them there?  You should net the pond to protect the fish.  Koi need ponds over 1000 gallons since they grow up to 3 feet long.  Your pond is too small for koi.  Mosquito fish normally breed pretty well but can be nippy on other fish.  With the fish you had, it's not a surprise that algae has done so well.  Is the algae short or long and stringy?  If it's long and stringy, it's hair algae.  Most algae-eating fish and snails don't want to eat that stuff.  Rosy barbs (tropical fish) may eat it.  If the algae is not hair algae but other attached algae, then a plecostomus may eat it.  They die below 50 degrees F but I think it's warmer than that there in winter?  To control algae, have lots of plants, shade, few fish, good filtration, good bacteria, and maybe some barley straw.  My page on algae is at http://www.fishpondinfo.com/plants/algae2.htm

Good luck!

Robyn