I have the idea which could return a great interest for pet shop keepers. Why not make tattoos on fishes? There could be any kind of tattoo... either a text (like "I love you", "Merry Christmas" or whatever) or a small picture. A customer would have an option.

I am thinking of creating some fish saving device. It can be an aquarium which records the water temperature, ph level, oxygen level, amount of food eaten etc. and automatically fixes the problem by adding food and/or by adding oxygen or heating the water according to the settings defined.

Do not fill an aquarium with water just after the purchase. If an aquarium has a frame and glass junctures are covered with putty or sealant, then let such an aquarium settle for a couple of days, change the water once a day. During this time, all toxins from putty are supposed to dissolve in water. Then wash your aquarium thoroughly, fill it with water and leave for at least a day. And only then put fishes into it. The water level in the aquarium drops over time... this is...