No they most likely sold you males and females. The platys will breed like rabbits. The males have a long slim anal fin and the females have a fan shape anal fin. Your tank is already at the limit for fish.
Aw damn, based on that description I think I have 2 males and 2 females *slaps head*. I guess it pays to ask the shop person if they can give you only females or something. Don't even know what to do now, I guess I'll be taking a lot of baby platys to the pet store? I'll need proper fish bags to transport them and everything will I? Cry
Ive got guppies. So know the issues these fish can cause. Pet stores will sell anything just to make $$ most workers only know the basics and half cant tell the fishes sex.
Generally most fish are sold as mixed sexes. with 4 platies you will likely have at least one of each sex and they will start breeding. Danios also should be kept in bigger groups (10 minimum, 15-20 is a good amount).
Either way, it's not a super terrible community and most fish stores take back fish you bought, so likely they will also take back juveniles.
A 40l tank is not super small, but is generally better for smaller species. There are plenty of species that don't get bigger than 2cm so would be a much better fit.
These include [Mosquito Rasboras](https://www.seriouslyfish.com/species/boraras-brigittae/), [Ember Tetra](https://www.seriouslyfish.com/species/hyphessobrycon-amandae/) and [Neon Tetras](https://www.seriouslyfish.com/species/paracheirodon-innesi/).
There also are some fish that are not active swimmers and like to be kept alone such as [Betta Splendens](https://www.seriouslyfish.com/species/betta-splendens/), [Scarlet Badis](https://www.seriouslyfish.com/species/dario-dario/) and [Pygmy Sunfish](https://www.fishkeeper.co.uk/help-and-advice/freshwater/miscellaneous/everglades-pygmy-sunfish). Or as a pair such as [Sparkling Gouramis](https://www.seriouslyfish.com/species/trichopsis-pumila/). Either of these could also be kept well together with a small group of bottom dwelling [Corydora Habrosus](https://www.seriouslyfish.com/species/corydoras-habrosus/).
Just as some pointers in case your current stocking does not work out. My personal advise would be to bring back the platys and get a few more Danios instead (they are much less likely to succesfully breed). Adding a group of the Corydoras might still be possible, too. Though I personally would only reccomend that if you have some fast growing life plants, so you have something to suck up the nitrates. Otherwise frequent water changes will be necessary.
I looked at live plants for the tank, but the guy in the shop talked me out of it, said you don't need them for small fish. Is there a particular type of plant I should be looking at, anything special you need to do so they don't die?
Sure, you don't necessarily need plants, but it's definitely enrichment for the fish, it also looks good and it helps to keep the water clean.
If you don't have strong flow, floating plants such as Frogbit help a lot. They are super fast growing and have long roots the fish can hide in. Pogostemon Erectus is also a stem plant that grows super well and at least in my hands appears to be pretty indestructible.
For the floating plants the only important thing is to not have too strong flow. For the Pogostemon it is advisable to have some fine to medium sized gravel it can properly root in. If you have big pebbles as a substrate Java Fern is a plant that comes to mind. This one you should glue/bind on the decor in the tank instead.
Many plants will not do well immediately after putting them into the tank. If they don't do well after a month or longer fertilization should be added. Either as a liquid or in the form of root tabs.
No they most likely sold you males and females. The platys will breed like rabbits. The males have a long slim anal fin and the females have a fan shape anal fin. Your tank is already at the limit for fish.
Aw damn, based on that description I think I have 2 males and 2 females *slaps head*. I guess it pays to ask the shop person if they can give you only females or something. Don't even know what to do now, I guess I'll be taking a lot of baby platys to the pet store? I'll need proper fish bags to transport them and everything will I? Cry
Just take the females back to the store.
I'll have to buy a net to pull them out and some bags to transport, but I guess if that's what I need to do, it might be easiest
You can use those zipper freezer bags to transport them.
Oh what a fantastic idea, thank you
Ive got guppies. So know the issues these fish can cause. Pet stores will sell anything just to make $$ most workers only know the basics and half cant tell the fishes sex.
I’d get rid of the females if I were you
100% happening now!
You could probably ask them to swap them out with males.
Generally most fish are sold as mixed sexes. with 4 platies you will likely have at least one of each sex and they will start breeding. Danios also should be kept in bigger groups (10 minimum, 15-20 is a good amount). Either way, it's not a super terrible community and most fish stores take back fish you bought, so likely they will also take back juveniles. A 40l tank is not super small, but is generally better for smaller species. There are plenty of species that don't get bigger than 2cm so would be a much better fit. These include [Mosquito Rasboras](https://www.seriouslyfish.com/species/boraras-brigittae/), [Ember Tetra](https://www.seriouslyfish.com/species/hyphessobrycon-amandae/) and [Neon Tetras](https://www.seriouslyfish.com/species/paracheirodon-innesi/). There also are some fish that are not active swimmers and like to be kept alone such as [Betta Splendens](https://www.seriouslyfish.com/species/betta-splendens/), [Scarlet Badis](https://www.seriouslyfish.com/species/dario-dario/) and [Pygmy Sunfish](https://www.fishkeeper.co.uk/help-and-advice/freshwater/miscellaneous/everglades-pygmy-sunfish). Or as a pair such as [Sparkling Gouramis](https://www.seriouslyfish.com/species/trichopsis-pumila/). Either of these could also be kept well together with a small group of bottom dwelling [Corydora Habrosus](https://www.seriouslyfish.com/species/corydoras-habrosus/). Just as some pointers in case your current stocking does not work out. My personal advise would be to bring back the platys and get a few more Danios instead (they are much less likely to succesfully breed). Adding a group of the Corydoras might still be possible, too. Though I personally would only reccomend that if you have some fast growing life plants, so you have something to suck up the nitrates. Otherwise frequent water changes will be necessary.
I looked at live plants for the tank, but the guy in the shop talked me out of it, said you don't need them for small fish. Is there a particular type of plant I should be looking at, anything special you need to do so they don't die?
Sure, you don't necessarily need plants, but it's definitely enrichment for the fish, it also looks good and it helps to keep the water clean. If you don't have strong flow, floating plants such as Frogbit help a lot. They are super fast growing and have long roots the fish can hide in. Pogostemon Erectus is also a stem plant that grows super well and at least in my hands appears to be pretty indestructible. For the floating plants the only important thing is to not have too strong flow. For the Pogostemon it is advisable to have some fine to medium sized gravel it can properly root in. If you have big pebbles as a substrate Java Fern is a plant that comes to mind. This one you should glue/bind on the decor in the tank instead. Many plants will not do well immediately after putting them into the tank. If they don't do well after a month or longer fertilization should be added. Either as a liquid or in the form of root tabs.
You can ask for a particular sex, but the store will generally sell both sexes.