Chinese Algae Eater. Unexpected Problem?

Unfortunately it's not a proper set up for your goldfish either. =( Three fancies would need a 75 gallon tank with double, maybe even triple, filtration. A single one of them should never be kept in anything smaller than 30 gallons, but prefer a 55 gallon. Otherwise you're gonna have a huge build-up of waste from their high bioload and more than rot problems. They cause constant spikes in water parameters and ammonia as is, especially in small tanks that are over-stocked.

As for your Chinese algae eater...I'm shocked he survived! They are normally fairly delicate and they do not like water as cold as goldfish do. They will also eat the slime coats of goldfish if not given proper foods, they need more than just algae or they'll switch. Put in some veggies(seedless green beans and cucumbers, heat them up good first so they're softer, spinach, peas once per week, cooked carrots on occasion and the like, or you could buy the Emerald Entree in the frozen fish food section, all your fish will like this stuff), and maybe some brine shrimp for him. The best option would be to find a pet shop that'll take it, you may even be able to get a little money for him at some shops. They sell pretty fast, so he should be alright. ^_^ You may want to look into re-homing the goldfish as well,t hey will not be ok for long like that. =( It was very nice of you to take them in though! It's just not a good set-up unfortunately.

And to Joylynn....teachers never do. They start up fish projects and go about it all the wrong ways. My friends school teacher did one and got ten mollies and five platies for a twenty gallon tank. All but one fish died within a couple months. I'm shocked they lived that long, seeing as a twenty can barely support five mollies on it's own, or five platies alone. Schools should be banned from getting "Pet projects" unless they actually know what they're doing. But this user was good about trying to take them home to help out. Most teachers toss them out if the students wont adopt.All the same, if the goldfish are kept in that small tank, they'll eventually die from toxin build-ups or over-cleaning and stunting.

You could check with your small, locally, owned fishstores and see if one of them will take them. Good luck, though, because Chinese Algae Eaters are nasty fish. Most people with aquarium experience won't go near them. Despite their name, they do a horrible job of eating algae. When they get older they eat the slime-coats off of other fish. If you really want to keep him then get a cheap 10 gallon kit for him - without other fish. If you don't want to do that then hopefully your goldfish will get big enough to eat him before he does any damage.

BTW - Comet goldfish (the cheap ones that are sold as feeders) grow to be over a foot long and the fancy goldfish can grow to 8 inches. I don't think your science teacher did her homework before picking the fish for her experiment. Feel free to call her out on that.