Great link Di - think you've put that up before
I love these fish - best algae eater on the planet if you get the right one!
As has already been said, you should never go by the common names and should really try and ID them yoursel (using Di's excellent guide) as a lot of LFS don't know what they are selling when it comes to these fish.
Crossocheilus siamensis is the one you want for algae. I have seen this labelled, siamese flying fox, siamese alagae eater and just flying foxes. In my opinion they should be called SAE, flying foxes are Epalzeorhynchus kalopterus - a rubbish algae eater that looks very similar (unless you know the differences).
As to behaviour - they are very aggressive towards other dominat males of similar species. You can keep them together but I would keep them in large groups of 5+, given the size they can get to (6+ inches), this means a big tank, the group does not stop the aggression but spreads it out. In very large set ups you can probably keep a couple as they will each maintain a territory. I had two in a 500 litre setup that basically staked out their territory at either end of the tank and left the other one to it. This set up originally had 3 but one was killed by the others - not enough space for three to cohabit peacefully. So i suppose either keep a large group or stick to 1 SAE per 200-250 litres volume
The older they get the more aggresive they get and even in groups you will sometimes get a problem with a dominant fish killing the others! Also the older they get, the less algae they eat, preferring more meaty foods(in my expereince) I have no idea why this is but a young SAE will survive on nothing but algae while an older one will switch to other foods!
As they get older and more aggressive they will also start to become a nuisance to your other fish - especially cichlids and dominant males of other species.
My advice - unless you have a jumbo tank is to only keep one and buy it very young. I have one in my Trigon with Discus and Clown loaches and apart from the occasional 'spat' between them there are no major issues. I bought him at about half an inch and he's now about 4 inches.
As an algae eater, my experience is they will eat any sort and vast amounts of it, I have always added one to every single new set up as the first fish to control the expected hair algae blooms.
Hope that helps
1xTrigon 190
3 Clown Loaches,14 Cardinal Tetras,8 Rummynose Tetras,6 Cory Trileneatus,6 Hatchetfish,4 otocinclus,1 SAE,1 Bristlenose,, 10 amano Shrimp, 1 pair Apisto Agazzizi. 3 Blue Discus
Anubius Barteri,Crinum thianum,Limnophilia sessiflora,Rotala rotundifolia, Echinodorus Blehri, Ech. Parviflorus,Ech. cordifolius, Ech. Tenellus, nymphaea lotus, Hygrophilia polysperma, Microsorum pteropus,Lilaeopsis brasiliensis
1xRekord 60
Blue Lobster, Flash plec
2 Anubias Barteri, 1 Microsorum pteropus
12 litre tank - 3 Glass shrimp, 4 japonica shrimp
1 Anubias Barteri, Riccia, Eleocharis acicularis
Coming Soon - Bluedave's 5' Bullnose Marine Divider (Watch this space!)