40 gal build

First of all I cant find my other post where we were discussing the fish to stock my 40 gal breeder with so if anyone finds it and wants to post the link that would be cool anywho so last week I got my 40 gal going with the sump and skimmer.  I used the sand and rock out of my 29 gal and added another 20 lbs of live sand.  Tested for ammonia nitrite nitrate this week and it never showed up.  While I was testing my 40 gal this week I had my fish in a ten gallon that I had set up and they were doing good.  The last few days I put little pieces of frozen food in the 40 to see if that would make ammonia show up or anything and it never did so I put the fish(two clowns) in the 40 and they look really happy.  Ammonia, nitrites, nitrates still showing 0 after 24 hours.  Ph is 8.2 and phosphates tested at 1.0 ppm. 

I added a firefish goby today and Im going to wait a couple more weeks I want to add some cardinals and this is where my question arises, can I mix cardinals example have a pj and a banggai?  I believe someone said I could in my other thread but like I said I couldnt find it :) Also how many fish are too many in a 40?  I know its all about how much my tank can handle (bioload)  but if I have two clowns, goby, 2-3 cardinals should i be done?
Thanks for your input!!

I guess it would depend a lot on the tank and what you have in it besides fish, but I'd say you have plenty with the 5-6 fish you have. You might get away with another smaller fish or two... but it sounds like you're getting close to your limit. 

You can def have 8-10 fish as long as they aren't big. I think I had 12 at one point in my 40 breeder. Even now I have 6 in my nano. Keep up on water changes and a large cleaner crew. As far as mixing cardinals I know of a few tanks that have a few different species in it.