Just finished up Episode 2 - 4 last night and found the information great. I had a followup question regarding levels. Several times you mentioned being within appropraite levels on nitrite, nitrate and the like, but what are the recommended levels? I know that some of this depends on your livestock, but in a reef tank with corals and inverts what are the levels you want to maintain. Thanks and keep the good stuff coming! :D

in a reef tank "appropriate levels" would be undetectable on a hobby test kit.

you want zero on both nitrites and nitrates, but not really possible- you should be able to maintain zero on nitrites and under 5ppm on nitrates. Small amounts of nitrates are ok. People will bioballs and other unnecessary filtration will commonly have over 20ppm.

Ph- 8.1-8.4
Alk- 3-4 meq/L or I think the other conversion is about 9-11 dkh?
CA- 375-450 depending on what u have in the tank.
Total and Free ammonia- zero

you want zero on both nitrites and nitrates, but not really possible- you should be able to maintain zero on nitrites and under 5ppm on nitrates. Small amounts of nitrates are ok. People will bioballs and other unnecessary filtration will commonly have over 20ppm.

Ph- 8.1-8.4
Alk- 3-4 meq/L or I think the other conversion is about 9-11 dkh?
CA- 375-450 depending on what u have in the tank.
Total and Free ammonia- zero
i wouldn't say its "not possible". my tank has NEVER shown a nitrate reading since the cycle.. :) and my tank before that was the same way.
but i will say its harder in small tanks...

i do agree with your other parameters though.

once should always strive to keep nitrite and nitrate at 0.

I do remember reading somewhere that said readings of about 5ppm are ok and they are maybe good for the tank? Not sure, I would have to look that up. If you have 5ppm- you know u got plenty of food in the tank- extra munchies during the day are always good. But having zero is better than have 10ppm or something too high.

yes, nitrates are ok and helpful to certain livestock in trace amounts.
but anything that can be detected with a hobby kit is "technically" to high.

will the tank be fine? sure.
"most" inhabitants can survive with a nitrate levels up to about 5 ppm, but that's not optimal.

if you are reading 5, you should work to reduce it, but not freak out as you should if you read 10, 20 or more..

two points i want to make.
1.) you "can" achieve 0 nitrates.
2.) Gwen is right that most tanks will do just fine with a reading of <5ppm nitrate, but you should still work to reduce.

once you get into the more advanced invertebrates, then even 5ppm of nitrate "can" be too high.