These are the little blighters!
http://www.thetropicaltank.co.uk/Fishindx/algeater.htm
Usually known as sucking loaches in the UK and Chinese algae eaters in the
US!

They get aggressive as they grow and prefer to feed on the slimecoat of
other fish.

I often see them in Malawi tanks - they are cheap and tough and more often
than not it is the only place people can put them. Horrible fish IMO.
If you visit the temperate house at Kew Gardens there is an indoor heated
pond that has loads of them - up to about ten inches long.

HTH
Sue