High Nitrates and low PH!

the calciums is a bit to high. You need to balance your alkalinity and calcium to stabalize your ph. Nitrates water changes with RO water should lower them down. Nitrates are the end of results of your nitrogen cycled so expect alot during this last few days of cycling.

Nitrates at 20 ppm are nothing. That is absolutely no concern. How are coral looking? My guess is that they are fine. Case dismissed.

But,
Bob said it, Alkalinity is missing in your test results. If you did not know it, Alkalinity is one of the four most important water parameters. As Santiago and Bob both indicated, the fact that Calcium is at 500 and pH is low is a sure indicator that Alkalinity is low. Check the Alkalinity ASAP. I'll bet it is below 8 dKH. That is too low. Low Alk is not an immediate problem but over the long term can be a real problem. I agree with Bob, it should be raised to about 10 dKH. It can be raised by 1 degree per day. If you need to know how to raise it, look a few posts down into the thread linked in my signature line.

Some sand may mix together, but most of the time different size sand particles separate into fairly distinct layers. The reason is because small particles fall down through the spaces between the larger particles. This is actually a good thing. Smaller particle sand offers more surface area for bacteria to populate, so it has more biofiltration capacity. As Bob said, it handles Nitrates very well. It will take about a week for the new sand to populate well enough to start making a difference. Your tank will be okay until then.

A last comment about the sand- If the sand was called "live" with "live bacteria cultures", that could also be a reason for the problem. Just so you know, the LS in your tank is more alive than that stuff. We often comment that a cup of LS from a tank like Bob's has more life in it than an entire bag of that "live" sand. New clean sand is a better thing to add than packaged LS. Don't get me wrong, I love CaribSea. I have spent time with the owner. But be careful that you find out the truth about which products are needed for each particular purpose.

So in summary, The water is not so bad and the sand will soon settle in and do it's job. You really have nothing to worry about.

BTW, water changes will not help here. Some would say that water changes cannot hurt. That is certainly true but why waste time on something that is not going to make any difference in the current situation.
To help understand this we need to look at the numbers. The Nitrates are at 20 ppm. A 15% water change will reduce Nitrates by only 3 ppm. Nitrates would then be at 17 ppm. From 20 to 17. That's it! That is truly insignificant. Seriously, the tank will not notice the difference.

Honestly, if the Nitrates were above 50, then is when I would worry.

If it was bad like that I would suggest this:
The best way to reduce all three N compounds quickly and continuously is with Algae. Algae is the answer. Algae eats Nitrogen compounds like crazy. Illuminated Macroalgae can reduce N by 25% in just a day and if lighted 24/7 can soon reach a point where it eats all the Nitrogen as fast as it is produced.

One more thing may be contributing to the low pH - Lack of gas exchange.
Gas exchange occurs at the water surface where CO2 leaves the water and Oxygen enters the water. If the water is not moving fast at the surface or if there is a glass cover over the tank the CO2 cannot leave. In other words the tank cannot breath and this creates a problem. So first, remove any glass that may be covering the top and second, be sure to have water being pushed from the bottom up to the top so that it roils. Here is a pic of roiling water.




Edited by Mark Peterson - July 16 2010 at 11:58pm

Honestly, I really don't see a problem. You can use the rest of that sand.

Or you could give that sand to someone just starting a tank and come get some Oolitic sand from me. Oolitic stays on the bottom, underneath larger particle sand. Just 1/2 inch of Oolitic sand on the bottom does a fantastic job, more than doubling the biofiltration capacity of the existing sandbed.