How big is it? How many chicks? Where is it, in some place climate controlled? How are you providing heat?
Some people successfully use aquariums but the biggest problem can be overheating. Too much heat can be as dangerous as too little. To me the ideal brooder keeps one spot warm enough in the coolest conditions and cool enough in the warmest conditions. This is easier to do in a climate controlled area than where you can get big temperature swings. If you use a heat plate or heating pad for the supplemental heat and it has great ventilation up high an aquarium isn't too bad, but if you use a heat lamp or incandescent bulb a smaller aquarium can easily overheat.
Chicks grow very fast. A smaller aquarium can get pretty crowded pretty fast. Another reason size is important.
If you clean and sterilize it the fact that it is used should not be a problem.
Under the right circumstances an aquarium can work. What circumstances do you have?