If you are willing to drive into the city, Old Town Aquarium on Wells and Chicago Aquarium and Pond are both incredible. I bought 2 beautiful German blue ram juvinelles at CAAP for $8.99 each. I was at OTA about 10 days ago and they had BALLOON blue german rams for $15.99 each. If your near Park Ridge, Living Sea Aquarium is also great. They have a cool shark and ray pool.
All three places are not cheap, but the quality of their fish makes it well worth it.