badfish

my wife and I decided to try setting up a saltwater tank. I bought a used 125gal tank with stand that was too good of a deal to pass up ( we were originally going for a 50- 70 gal). We are giong to take our time setting up and researching, about 3 months untill the new room is done. The cost involved with a tank this size is steep so we are starting with a fish only tank, hoping to slowly convert live rock and coral. I have been doing a lot of research but the more I do the more conflicting info I get. I have a list of the basics I will need, good skimmer ( Aqua C?), test kits, buckets, meters etc. Some questions I havent seen yet
1. Can I incorporate less than recommended amount of live rock and slowly add more? Maybe 1/2 pound per gallon and add more at later intervals? The rock alone for this tank would run me at least $800
2.with the live sand and good skimmer do I also need a filter system?
3. Is one skimmer good enough for a tank this size
4. How many powerheads for a tank this size and any recommendations on brands
I'm sure I'll have plenty more questions, just in the planning stage now.

agsansoo

1. Yes. You can add the live rock in stages but you must keep a close eye on you water parameter very closely.
2. Live rock/sand is your filter system, that's why it important to have enough (see question 1)! So adding a power filter or a protein skimmer will help until your water parameters stabilize.
3. Yes. One skimmer rated for your tank size in all you need.
4. You need around 20 times your display tank volume (125g tank = 2500gph). So two Hydor Koralia-4 (1200gph each) powerhead pumps is a good start.

badfish

The local fish store said I could get away with just live sand in a fish only tank, thats why I was asking about less than recommended live rock.
Do I have to worry about different types of bacteria when adding rock in stages? I assume I should cure the rock in a different tank but do I use water from the main tank, mix new or does it matter?
Couple more questions: Is the an easier way to check for leaks besides filling the entire tank up? and any tips on cleaning, glass an frame have a white buildup (calcium?) and I don't want to use any detergents.

Oil_Fan

You can add the LR to a different tank and let it finish curing there. You'll know when the curing is finished when the ammonia, nitrates and nitrites read all 0. As for which water, I doubt it will matter. But if you're setting up a quarantine tank, then you'll want water out of your main tank for it.

To check for leaks, you'll need to fill it up. You could do it outside and just use your garden hose. That way if it does leak, it's not leaking all over the floor. Then just drain the water out.

The white stuff could be salt since this is a used tank. If water won't remove it, then try vinegar. I've heard that's good for removing salt build up.