Actually, sometimes, I think the fishes are just there to attract people and they make money from impulse buyers.
This scenario has been prolly repeated millions of times:
You went to the pet store to buy dogfood, or whatever the reason you went there...glanced at the fish section..Oh pretty!
You look around, saw colorful fish. Now youre thinking of owning fish. You talked to a guy who works there, and ask questions. The guy tries to help you. After 10 minutes, you decided to go for it. You bought EVERYTHING the guy told you is important for the fish's well being.
You bought a filter, a 10 gallon kit, including everything, decor, and everything you could think of "that'll help".Then you bought 2 of each pretty fish you liked. then you went home, filled the tank with water added the water conditioner, added the decor, then put the fish straight from the bag. Oh, so pretty! After a week, all the fish seems to be gasping for air, and you don't know why, after a day or so, they all died. You went back to the pet shop, and told them what happened. They said the ammonia might be the cause, and told you to change the water. You bought more fish, and this time, you bought not just two, but one more of each fish, to "keep them company". You went back home, then drained the tank, scrubbed everything clean with soap, filled the tank again, then added the little fish. After a week, the same thing happend as your first batch, then that gets you frustrated, and you decided not to continue anymore. Now your stuck with overpriced aquarium supplies who just collects dust in the corner.
Sounds familiar? to me it is, cos I was the guy who went that day to buy dogfood for his pooches. But i started it again, this time, a 75 gallon, runnig for 5 months now and I'm happy to say the results are amazing. The only difference? I 've educated myself.
Anyway, sorry for the long post.