cured rock vs. cycled tank

[troni]

I've been doing my due diligence and researching like crazy, granted I didn't read the stickys in the topic. Now I know you new to cycle and you need live rock as a main bio filter but if I were to put 80% base rock to 20% live rock to keep prices lower would I need to wait till the base rock is cured? Or can base rock have the correct bacteria on it to be cycled without being fully cured? Hope my Q is clear. Can base rock cycle a tank like live rock? When I start my tank I have to do this anyway so maybe ill do a experiment without harming any livestock of course.

[Myka]

Now I know you new to cycle and you need live rock as a main bio filter but if I were to put 80% base rock to 20% live rock to keep prices lower would I need to wait till the base rock is cured?

No, the base rock won't produce ammonia.

Or can base rock have the correct bacteria on it to be cycled without being fully cured?

Base rock doesn't have any bacteria on or in it. It should be fairly sterile, although it can leech phosphate and nitrate depending on the source of the rock. Some is simply dried out live rock which will be nutrient heavy (not good). Marco Rock seems to be pretty good quality as far as base rock goes.

Can base rock cycle a tank like live rock?

No, base rock doesn't have any bacteria on it to seed the tank with, nor will it have any die off to feed bacteria. Essentially, bacteria will colonize the tank eventually because nitriying bacteria in a small amount are airborne in "all" our air. Put a bowl of water out, add some bacteria food (ammonia), and nitrifying bacteria will colonize provided the food source continues. However, it will be very slow to get to a great population.

The more base rock you use the slower you have to be in stocking your tank. If you use say 20 lbs of live rock and 80 lbs of base rock you kind of have to pretend you only have a 20 gallon tank with 20 lbs of live rock in it because it will take quite awhile (weeks/months) for the bacteria to colonize the base rock. It will take about a year for the base rock to be fully colonized including DEnitrifying ANaerobic bacteria in the center of the rocks. The denitrifying bacteria process nitrate into nitrogen gas (and other things) that off-gases from the tank.

When you add a new fish to the tank the nitrifying bacteria will have more food (ammonia from the fish poop/peeing), and it will take awhile for the bacteria population to increase enough to handle this added ammonia. This is why we have to stock slowly.

[troni]

But correct me if I'm wrong denitrifying bacteria will colonize on any surface so whether the rock is alive or not shouldn't make a difference? Oh and to do the cycle I would be throwing in a deli shrimp so that would start the cycle

[Coralgurl]

I started my tank with 20 lbs of live rock and let the tank cycle. As I started adding more fish, I noticed that I was having algae issues in the tank, so added another 10lbs of LR and 30 lbs of base rock in August this year. the base rock went through its only little cycle with the start of bacteria growing on it, went neon green and now has corriline algae growing on it, but it is nowhere close to looking like the original LR, even the rock added in August. The bacteria will grow, but it takes much longer for the base rock to become effective as Myka noted. I expect its going to take a few more months but its getting there. I believe it is providing some filtration, but maybe 25% after 2 1/2 months.

Take it slow and don't try to rush the cycling or addition of anything to your tank. You may save money on the rocks, but it will cost you down the road to go too fast. I'm a newb too and I have learned this the hard way.

[troni]

Ok I see what's being said thank you for clearing that up.