Female dalmation molly & male crowntail as tankmates?

[CTBettaLover]

Hello! After researching a little more I have realized that my pet store may have misinformed me about keeping a dalmation molly. I have since learned that mollies do best in a minimum of 20g. However she is pretty small. Anyone know how big dalmations get??
I have her and 3 bronze cories in a 10g tank that used to be my male blue crowntail's personal tank. He has been in a hospital tank for some time now. He is starting to recover and I wanted to eventually reintroduce him into the 10g. It is heated unlike his hospital tank and it is starting to get cold so his ht is getting around 72F. No bueno!
Im afraid that the molly is going to pick on my betta. I know that it is usually the other way around but my betta is quite small and not overly aggressive. I know this because he has interacted through the glass with my boyfriend's much larger male blue crowntail who is always pissed at something. Whether it be my fish when they get some viewing time, or his own reflection no matter what backdrop or block from light we try. My fish will puff up but eventually back off. Where as my boyfriends large crowntail will sit there pushing his nose into the glass back and forth flaring like crazy for a while. Once we seperate them he will even pace back and forth in that spot looking for my betta. Mine may only back off because he is much smaller than the other but he rarely flares at his own reflection. He doesn't seem to have much of an interest in fighting, he'd rather be wiggling at me. :)

Anyway, at feeding time when I first put the molly and cories together, I noticed my molly chase the smallest of the cories away from an algae wafer before but never nipped at him. I just dont want her to nip my poor lil betta. I haven't seen much aggression from her since. Im guessing she's a girl bc she doesn't have a tube like fin on her belly. She has two rounded fins. Am I correct in this assumption?

Anyway, any feedback would be greatly appreciated! Happy fish keeping! <3

[asukabetta]

I'd say... why risk it?

Mollies tend to prefer harder water which is the opposite of what betta's like, also they can be confused as rivals due to finnage though short finned molies have less chance.

If you think about it, it's not only about the molly who can bully smaller fish (even though you said he didn't nip) you betta could get into a fight with it. It is also said that mollies do not like just like bettas having fish with fancy tails, thus the risk.

10 G with that many fish -- I do not know if it is overstocking or not, however it may not be enough space to add the betta in a way he can hide when threatened or scared besides it seems you have met your aquarium space limit with the molly, just like you said they need around 15-20 gallons, and they can grow about 6 -5 inches big.

[CTBettaLover]

Well my water is pretty dang hard. I thought that was good for keeping stable water perams? I know bettas and cory cats cannot tolerate aquarium salt where as mollies sometimes do better with a little supplemented in their tank. I went to PetSmart today looking for a cheap 5 gallon tank kit for my female bettas and found so many different types of mollies! The black and dalmation mollies were listed as min. 10g tank size? I would really like to keep her but I don't want her to suffer if the conditions aren't right. Im not quite sure what to do. I think I am going to introduce my male crowntail to the 10g and see how they interact. If all goes well, I will hope for the best but still keep an eye on them for signs of aggression towards eachother. If they end up not getting along I think I will have no other choice than to return her to PetSupermarket. Does anyone know if pet stores will take fish back without a receipt?