qustion on live rock
 

ok i have about 35 lbs rock in my 90 gallon tank and thinking about getting about 40 lbs more .sould i buy all the rock at once or will there be to much of a spike in my tank for fish to live?was thinking about 20 lbs one month then 20 later

I would do what you are thinking and add 20 lbs this month, then 20 lbs next month... though it would be better if you only added say 10 lbs at a time. Add some rock, watch your parameters, when things stabilize add more rock. Adding too much will probably spike the tank, as you suspect.

If i were you I would buy all the rock you need, and get it to cycle in a Rubbermaid tub outside of the aquarium. Once that cycle is over it will be safe to add it all to your tank at once. Check out the link in my signature for more information on cycling rock outside of the tank. :)