Hi there! I'm pretty new to the hobby and started with a 6 gallon Nano. I'm totally hooked and of course am looking to upgrade. Due to space limitations (and of course budget issues...) I probably can't go larger than a 40 gallon tank with a 10 or 20 gallon sump. I saw several people saying a 40 gallon breeder tank was a great tank to start with but was't sure what a breeder tank was or the dimensions of this type of tank. Also, are there good online sites that anyone recommends regarding purchasing tanks/sumps? Thanks for your help!