That seems a little bit on the small side to be keeping clown loaches in for any long period of time - I wouldn't do it unless you have a larger (like a 55 gallon) tank to move them up to once they hit 4" or so. But even a 48" tank is going to be too small to keep a full-grown group of clown loaches. One way you could do it is try to sell the loaches once they outgrow your tank, then use the money to buy more small ones. The usual size of clown loaches I see in stores is about 1", so some people might well be interested in buying larger ones from you. But for now, you should be fine with them as long as the water chemistry isn't too big a shock!