~If you have a curious cat you absolutely need a very sturdy aquarium hood.

~They are both ryukins just different colors. Buy two similarly sized and they won’t discriminate each other.

~ The usual recommendation for two fancy goldfish is a minimum of thirty gallons.

~Chinese algae eaters may eat algae when young, but as they get older they become nuisances, plus they are tropical fish. The majority of algae eating fish are tropical and should not be mixed with coldwater fish. Scrapping the fish is really not such a bad chore. Algae should not be a problem so long as the tank is not overstocked, not near a heat source or window, and you do weekly water changes of 25%.

~I would be concerned about the stress from shipping the fish. I would first visit all your local pet stores and observe their available fish before ordering from the internet.
References :

Before I do this here are my questions to the experts:

-What is common in Ryukins, like dieases. And is it likely to get them even if you take good care of your fish?

-Would they do okay with my cat?

-If I purchase them for 5 bucks each at only 2 inches how long will it take for them to grow to be 8 inches?

-I want to get a Red & White Ryukin and a Calico Ryukin, they’ll do fine together right?

-What’s the smallest tank I could get.. 20-25 gallons?

-Could I put Algae eaters in the tank so I don’t have to scrap Algae.. if so what kind and how many? Chinese Algae eater?

Does anyone know of a good site that sells tanks? I’m going to order the fish from this site below but they don’t have big enough tanks.

http://www.liveaquaria.com/product/aquarium-fish-supplies.cfm?c=830+835

My last question is if ordering fish online will it shorten there life span?

Thanks!! Sorry for all of the questions