Is My Tank Over Stocked?

[0_Infinite_0]

I think I may have accidentally over stocked my tanked. 

 I have a 20 gallon tank with 3 Powder Blue Dwarf Gouramis. I'm new to Gouramis, but I do know there is a chance of them fighting. I've been watching them very closely and I have back up plans just in case! Today I picked up 3 Silver Lyretail Mollies and 3 Dalmation Mollies. I thought the Mollies where smaller than they actually are... I do have a female Betta, could I try to put some in with her?
 
Thanks so much!

 

[NickAu]

 
Powder Blue Dwarf Gourami

If they are 3 males it could be a problem.
 

 
Today I picked up 3 Silver Lyretail Mollies and 3 Dalmation Mollies.

A 20 g is about 2 foot long? IMO too small for mollies, The females grow big.
 

 
I do have a female Betta, could I try to put some in with her?
 

Bettas like soft water Mollies like hard water, Plus your Betta may not like or want tank mates,

 

[Byron]

I concur with Nick.  You should ascertain your source water parameters.  If you are on municipal water, check for their website and see what the GH (general hardness), KH (carbonate hardness or Alkalinity) and pH levels are for the water.
 
A 20g is a very small space to fish, and though they are likely small now (fish in stores are usually very young) they will need space to grow.  Mollies will outgrow this tank fast.  And the Betta is not a community fish (assuming this is a male).
 
Byron.

 

[123Sam123]

Fish typically need 20g of room for the first, and add 10g for the rest, however this changes depending on the variety of fish.

 

[Essjay]

Those tank sizes are for goldfish. Tropical fish, on the whole, don't need the same as goldies.

 

[Fishmanic]

I have 10 small fish in a 10 gallon for a month now and they do fine. I have 5 harlequin rasboras , 4 julii corys, and one dwarf gourami. Nitrates, with 40% water changes in this well planted tank dont get over 25 ppm. When you stock a tank, you have to take into consideration their size when they get full grown. I consider my tank to be fully stocked now.