Are Bigger Fish Just Older? Or Different Types?

Sorry if this is a daft question. My LFS has one tank of harlequin rasboras that are the standard small sizes I'm used to seeing in pet shops. They have a separate tank labelled "large harlequin rasboras" full of much larger ones. Same for neon tetras and cardinal tetras etc.

Are there different breeds within each species that grow bigger? Or are the smaller sized ones just juveniles and the bigger ones full grown?

(I know I could just ask the LFS but they have a history of just making things up... yet they are the best in the area... sigh)

 

The smaller ones could be lambchop rasboras, and the 'large' are just regular harlies.

 

Thanks, good thought but they have a separate tank for lambchop rasboras so it's not that!

 

Some LFS buy different sizes of fish and sell them at different prices. Ive seen this happen most often with angelfish and goldfish. IMO I don't know why they do it with fish that tend to look the same as they get larger as I feel it wastes tank space that they could have a different species of fish instead.

 

The larger ones tend to be older fish. They may have received two different imports and paid different prices for them (hence not mixing them). Shipping is a big part of fish costs, and larger fish cost more to ship.

 

Thanks. Good to know they are probably just older. I actually like the look of the bigger ones more, but if they are just older I'd rather buy the younger ones and grow them up in my own tank

 

A lot of people fear small ones will be eaten, and many more are impatient and don't want to grow their fish or have them for years - they want ornaments now.
I had some cardinals I bought small and grew, and it was fun. They became huge and lived for many years as a group.

 

Any tips for successful cardinal keeping? I would love some but have heard they are not very hardy.

 

I find cardinals easy. You need large tanks (a 36 inch/one metre tank is good - but it's good for most small fish). Large groups. Weekly 30% water changes. No crowding, but a social group of a dozen or so. Varied diets. Warmth (24-26c). Planted tanks so they will feel secure and be able to act naturally.
With that, you can have them for 5-7 years.

 

yea there are all sorts of reasons to buy larger fish instead of smaller fish. Even a pleco, which we often see as small fish first, could be bought at a larger size for a larger tank, rather than waiting for it to grow.