new set up-frontosas and compatibility

Question
I recently got a used 55 gallon tank and i just finished cleaning testing and resealing it. I wanted to set up a frontosa tank. I do underswtand after a lot of research that iot will eventually be to small for them but its all i can afford for now but definitely plan in th enext year to get a larger tank.
My first question is i have a tank that i used for my crayfish and some fish. My crayfish died and i was going to get rid of the tank. is it ok to take the water from the 30 gallon and transfer (the clean top water) and eventually the vacuumed gravel over so i could have some good bacteria in the water...or should i just start from scratch. (the water is tested and levels are good)
Then i was thinking of substrate and confused what is ideal for frontosas. If i do crushed coral (mixed with the other gravel) will that make the PH to high... can i use sand or is that to hard to work with.  
Is there a way to sex a young (1-1.5 inch) frontosa as i ideally want 1 male 3 females.
In the 55 should i just keep those 4 or can i add a few young calvus?
and not to push my luck but do you know anything about these diy backgrounds made from styrofoam and cement ( http://www.cichlid-forum.com/articles/diy_background.php )
you think cement is safe to use?
thank you for your time and help

Answer
Hi Gil,
 Using some water (say 5 gallons) from the old tank should be fine.

 I don't think you can have pH too high for frontosas.  I would go with crushed coral.

 Sexing young cichlids is largely a guess.

 Personally, I wouldn't put in calvus with frontosa.  Keep in mind that frontosa are highly predatory fish.

 I would be very cautious with cement.  It leaches out chemicals for a long period of time.  HOWEVER, given that you want a high pH, calcium rich, environment for frontosa, it MIGHT be okay.  Personally, I would be reluctant to do that if I had just spent many hundreds of dollars on frontosa, but the choice is yours.

 Speaking of which, I strongly urge you to get good frontosa. Frontosa are a long-term fish, and you will likely have them for 5 to 10 years so get good ones to start with.

-- Ron
  rcoleman@cichlidresearch.com
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