i have 4 clowns in my tank a skunk ,a mated pair of cinnamons,and a large tomato.they honestly hate each other and stay to their own sides of the tank if one leaves and crosses anothers territories they attack, so the skunk stays in his anemone and the pair in the middle with the tomato on the end if my tank wasnt 6 ft long im sure they would kill each other over night.in order to get clowns of diff kinds to stay alive in the same tank you will need lots of hiding places and space, feed them where they are dont force them to leave their territory,if a fight breaks out split them up for a bit before someone losses a fin or dies.having them host things is good and bad they want to protect their investment so when another clown comes around they will fight honorably so i keep a number of things for them to host if need be.

in all honesty in a 20g tank i would stick to the less aggressive species or stick with the same ones or a tank divider they are easy to install in a small tank i had to go that route once and i just cut small holes in the divider to keep water flowing good.

Guys...
You are not guaranteed aggression from clown just because you are putting them in a smaller tank together.
When they are added, the level of each ones sexual maturation and the overall size of each specimen play major roles in whether they will form a family unit or not.

There are no guarantees one way or the other.

I say you rescape and give it a shot but be prepared to pull out any fish that gets rejected by the mature female.

I highly reccommend picking up this book
http://www.jlaquatics.com/product/li...tcover%29.html

and doing some reading on clowns and then based on your interpretation of the facts, do whatever you think is viable

i totally agree with gobytron your not guaranteed aggression and your not guaranteed acceptance you can only try and see what happens if you lose a fish lesson learned if they thrive then another lesson learned.

well after a long debated trip to the fish store i decided to buy the clowns and see what happened. here i am 2 days later and everyone likes eachother. no aggresion, and everyone has their own sleeping space :)

I have 3 False Percs in my 210g mixed reef with no problems. Sometimes they all go in the same anemone. Sometimes they pair off. Sometimes they each take a different host. No rhyme or reason. No problems or aggression. Luck of the draw.

Anthony