#6 is Poecilia sphenops (black form), the "black molly."

Thank you, Michael. Can you please tell how to make difference between P. sphenops and P. velifera?

Poecilia sphenops has only about 9 rays in the dorsal fin, whereas P. velifera has 15-21 rays (usually 17-19). Source: R.R. Miller (2005), Freshwater Fishes of México. (Cannot actually count rays in the dark photo, but the dorsal fin base appears short. Perhaps you can verify the approximate count? P. velifera looks like this: https://s-media-cache-ak0.pinimg.com/originals/d0/25/3f/d0253fd6ee1f3da9625717628819edca.jpg )

 What is the species?

# 1, 2 and 3 : Xiphophorus maculatus = Platy

# 1 and 3 : Platy "tuxedo red"

# 2 : Platy "red Mickey Mouse"

In the First serie :

# 3 : Ancistrus gold female (Loricariidae)

See : http://www.aquavipare.fr/reproduction_ancistrus_gold/reproduction_ancistrus_gold.php

# 4 : Corydoras aeneus var. albinos (Callichthyidae)

# 7: Tethia conchonius (Barbus conchonius)

What is that species?

Botia (lohachata?) (Cobitidae ; Botiinae)