shouldnt be i mean i got 10 endlers and 8 corys and some shrimp going in mine maybe 2 dwarfs only thing is some ppl might give you "grief" over putting the angle in that 30 if its not 18 inches tall i think ....but i wont ...im not a hundred percent sure on this but if your fishless cycling your new tank (witch i hope you are) you could probably do 2 dd (male and female) 2 angels (male and female) and 5 tiger barbs (2males and 3 females)....and one last bit that i forgot im not so sure about the barbs going in the tank with the angels and dd's as tigers are fin nippers but if the two you have now have "grown-up" with these they might be fine but i would watch out for the new ones thats the only thing negative i will have to say about your set up is you probably will run into issues with your tigers harrassing your dd's and angels, you might have to choose witch you want to go with