...When your wife no longer asks "what ya doing?" and instead asks "what's the thread you're reading about?"
...When you teach your two year old to count using the guppy fry in your tank...
...when you see someone looking at a used tank in a second hand store and immediately ask them if they are actually going to buy it, cause if they don't you will, and then stand around for 20-30 minutes 2 aisles away to see if they actually do buy it...
If wishes were fishes... I'd need a few more tanks!