GSP not growing.

[Pufferpunk]

Yes, it will keep your nitrate high, unless you do many WC & rinse the media often. You are trying to alleviate that bu making this tank SW.

[Aquarist]

How expensive is LR rubble?

[Pufferpunk]

Probably cheaper than larger rocks. Or just take a hammer to a larger one.

[jus85411]

some pet stores around me sell rubble for $2 or $3/pound. call around and check out prices. it might be cheaper for you to look on craigslist for someone with dry rock and you can make sure its clean and take a hammer to it from there

[Aquarist]

I have four pounds of real live rock. However, being brackish, i'm not sure if it's alive. Once it's saltwater. Can I just take that out and crush it up? Or should I find different pieces.

[Pufferpunk]

That would be fine.

[jus85411]

essentially wont the rock, no matter the SG since its providing a surface area with water flow, be considered "live" rock?

[Pufferpunk]

Not really in the definition of marine LR, which contains all sorts of creatures.

[Aquarist]

The protein skimmer has been ordered, I now have questions.

#1: Do I run the protein skimmer and Aquaclear 70 filter both 24/7?
#2: The filter currently has freshwater media and cartridges, which do I take out. How do I crush the Live Rock, what is the purpose of LR rubble in the filter.
#3: is a 300 GPH filter sufficient for a 55g saltwater tank, provided I eventually add powerheads etc?
#4: Will I kill my cycle by taking out this mature media out of the filter and tossing in Live Rock rubble?
#5: My meter says the puffer is in 1.021 SG. I will also take it to the LFS to get it tested, last time I had it tested at LFS, my skimmer showed 1.016, theirs showed 1.012 - who's is correct?
#6: Is 1.021 a proper longterm salinity for a GSP? Should I raise it to 1.022?
#7: For a 2.5-3" GSP in full saltwater, is a protein skimmer, filter, some live rock, and weekly partials of about 20% enough to keep nitrates proper?
#8: What kind of test kit should I get?
#9: Would a Yellow Headed Jawfish be possible in this tank? *I have a one inch deep sand bed, and I know they can go under the sand bed in about a millisecond if needed. But, I don't want to jeopardize either fishes health. I'm just brainstorming here, I doubt this will be possible. The puffer is very hostile.*
#10: How do I know if my salinity is proper to add lots of Live Rock? I currently have four pounds in there, which I have had since 1.012, and it now grows lots of algae, wormy looking things, and any other strange stuff you can imagine. But, I realize LR at under 1.020 can be hazardous. And, according to my LFS, the SG may only be 1.017 when tested, would it still be safe to add Live Rock at this gravity?
#11: I have a lot of fake plants in this tank, along with caves, etc. When I add more Live Rock, I assume I take all of these decorations out, and then fill the tank with lots of Live Rock?
#12: Is one airstone and a filter proper circulation for a full saltwater tank until I can get a powerhead or two, etc?
#13: Any more info you can provide will be helpful. Thank you kindly.

[Pufferpunk]

#1: Do I run the protein skimmer and Aquaclear 70 filter both 24/7?
No need to run both. The live rock should contain all the beneficial bacteria you need.
#2: The filter currently has freshwater media and cartridges, which do I take out. How do I crush the Live Rock, what is the purpose of LR rubble in the filter.
Extra surface area for bacteria to grow & a great place to grow pods, which eat detritus.
#3: is a 300 GPH filter sufficient for a 55g saltwater tank, provided I eventually add powerheads etc?
i'm not sure but I think 10x turnover rate is the requirement.
#4: Will I kill my cycle by taking out this mature media out of the filter and tossing in Live Rock rubble?
Nope, not if the rubble comes from an established system.
#5: My meter says the puffer is in 1.021 SG. I will also take it to the LFS to get it tested, last time I had it tested at LFS, my skimmer showed 1.016, theirs showed 1.012 - who's is correct?
Sounds like one or both of those hydrometers aren't calibrated. You need to purchase calibration solution for this:
http://www.shop.mediabaskets.com/Pinpon ... 1-15mL.htm
#6: Is 1.021 a proper longterm salinity for a GSP? Should I raise it to 1.022?
Anything 1.020-25 is fine, to make the skimmer work properly.
#7: For a 2.5-3" GSP in full saltwater, is a protein skimmer, filter, some live rock, and weekly partials of about 20% enough to keep nitrates proper?
In a 55g, that should work but you'll need to check your nitrate occasionally, until your puffer is a full grown adult.
#8: What kind of test kit should I get?
API SW.
#9: Would a Yellow Headed Jawfish be possible in this tank? *I have a one inch deep sand bed, and I know they can go under the sand bed in about a millisecond if needed. But, I don't want to jeopardize either fishes health. I'm just brainstorming here, I doubt this will be possible. The puffer is very hostile.*

The puffer is very hostile

You just answered your own Q.
#10: How do I know if my salinity is proper to add lots of Live Rock? I currently have four pounds in there, which I have had since 1.012, and it now grows lots of algae, wormy looking things, and any other strange stuff you can imagine. But, I realize LR at under 1.020 can be hazardous. And, according to my LFS, the SG may only be 1.017 when tested, would it still be safe to add Live Rock at this gravity?
I think >1.018 should be OK.
#11: I have a lot of fake plants in this tank, along with caves, etc. When I add more Live Rock, I assume I take all of these decorations out, and then fill the tank with lots of Live Rock?
That is preferable but it's your tank, decorate as you please!
#12: Is one airstone and a filter proper circulation for a full saltwater tank until I can get a powerhead or two, etc?
I wouldn't use an airstone in SW, it's gonna make a salty mess.
#13: Any more info you can provide will be helpful. Thank you kindly.

[Aquarist]

So, all I do is basically buy 2-3 more LBS of LR from my LFS for a few $. And instead of putting it in the tank, take my media, cartridge, and everything out, take a hammer to the larger rock, and fill the whole filter with Live Rock rubble? Or is their some sort of saltwater media I will still be using?
Also, as far as me not running the skimmer and filter at the same time, then what is the purpose of filling the filter with LR rubble? Just curious, not exactly sure how to set the filter up. If I use media, cartridge, or just full of LR rubble.. Thanks again.

[Pufferpunk]

Just rubble, nothing else in there (you can use the "basket"). I bet the LFS will happily sell you their rubble, so you won't have to break up a rock. Probably cheaper, too.

[Aquarist]

LFS suggested not using rubble for surface area unless I have 10 or more pounds, something like that.. They said fill the tank with LR, run the skimmer, and use a foam in the aquaclear and rinse it every 3-10 days. And my Nitrates will stay low.

[Pufferpunk]

Then listen to your LFS, what do I know???

[sevenyearnight]

LFS suggested not using rubble for surface area unless I have 10 or more pounds, something like that.. They said fill the tank with LR, run the skimmer, and use a foam in the aquaclear and rinse it every 3-10 days. And my Nitrates will stay low.

A LSF is a business, they are there to make a profit. Of course they want you to buy more rock, their advice will benefit them financially. PP has no ulterior motive for her advice. It's your choice who you trust.