Aggressive Algae Eater

[Hollyweb]

A couple of weeks ago I brought some new fish home from the pet store. I got 5 harlequin rasboras, and 3 variatus platies, along with 2 algae eaters. One of the algae eaters went into a 5 gallon tank with a betta and the other algae eater went into my 20 gallon tank with the rest of my fish.
 
The algae eater with my betta seems to be doing just fine, and cleaned up my tank very nicely in one night. The other one is also a busy little worker bee fish, but I have noticed that he also goes after my other fish and it looks like he is trying to latch onto them with his sucker mouth. Tonight I came home and one of the variatus look like his dorsal fin got caught and tore where it meets his body, and I noticed that one of my guppies in that tank has a round spot on the side of his body where it looks like maybe the algae eater rasped him.
 
I don't think it's any kind of fungus because none of the other fish are displaying any kind of similar spots on them. Should I remove the algae eater from my tank? I heard they could be aggressive when they get older so I thought they'd be okay for now.

 

[Gruntle]

Sounds like you have a Chinese Algae Eater, and yes, they do that. Best to re-home him if you can.
 
Personally I can't understand why they're sold as algae eaters, because they don't eat algae after a while, and instead eat fish. I'll never get another one.

 

[Hollyweb]

I prefer otocinclus but they were out and I haven't had much luck with them. They seem pretty delicate and the last one I had lasted only a couple of months. But I haven't had much luck with plecos either.
 
What kind of tank would a Chinese algae eater be best in?