Ammonia / Nitrite levels

It depends on how the tank is set up.
Just a warning though, if the tanks are less than 4 months old it may not be over for either of them. But there is an easy way to avoid problems.

In general the more Live components used, the less problems with Nitrogen levels. This is the reason I put together the Reefkeeping Tips thread linked below.

A really good method that helps the tank fully stabilize during the first week of it's life is the use of good amounts of Macroalgae with continual illumination when necessary. Macroalgae is easy to get here because hobbyists on this MB are always harvesting it from their systems.

Macroalgae with 24/7 illumination is the best thing for emergency reduction of Nitrogen pollution.

How much Macroalgae was added to these tanks?
Algae, when illuminated all day or in extreme cases at 24 hours per day will eat up Nitrogen pollution like crazy, before it becomes a problem.

While algae keeps N levels within limits, the good water quality allows other biofiltration organisms like bugs, sponge, worms, etc., to flourish. This helps a tank mature to where the algae can be harvested/reduced and given to other hobbyists for their new tanks.

Can you post a pic of the tanks, or are there pics in another thread?

Thanks for the pic. Wow, you are naturals at aquascaping. 
In a newer tank like this, things are struggling and some stuff on recently added LR may die, causing a spike in pollution levels.

I would get more Macroalgae, Caulerpa for sure.
As Caulerpa grows and covers the rock it looks awesome and when the time comes to harvest it, that would be the time to add that Tang or Rabbitfish you've been wanting. The abundance of Algae will not only handle the pollution from unexpected die-off and from the new fish but will be like a continual feast for the fish. Fish added to an algae-ful tank are much less likely to stress and die. This is the best way I know to prepare a tank for adding it's first fish, especially it's first herbivorous fish.

Here is what a tank can look like when there is plenty of Macroalgae.

Where's Waldo? Can you find the five types of algae in this picture?

Those young Bangaii Cardinal were transported when they were just half that size, from Farmington UT to St. George UT and not one was lost, partly because they went into this algae-ful tank. Cardinals are carnivores rather than herbivores, but they benefit from an algae-ful tank because of the bug population. Bugs grow great where there is plenty of cover and food. The bugs I'm speaking of are Amphipods and Copepods.

For a new tank like yours, I would not recommend a Purple Firefish. Firefish are too delicate and Purple Firefish are more expensive. Let the tank grow for 2 months with plenty of algae OR chose a different fish to start off with now, one that's less delicate, but not a Damsel, except maybe a pair of tiny Yellowtailed Blue Damsels.

Just a note before I forget, it's not necessary to "Quote" the previous post, rather, click Reply or use the Reply box at the bottom.

How many snails are in this tank?
What powerheads are in this tank? I can only see one in the pic.
If it were me, I'd stop using the external filter. It's unsightly and only going to cause problems, if it is not already a source of problems.

I know I say a lot and border on being overcritical so if you don't want this much information please let me know. Would you care to share a pic of the other tank?

Forgot to mention - 

Wonderful.
Thanks for the explanation and the other pic. The picture quality is just fine. I have seen enough tanks and pictures of tanks to be able to see what's going on. The things that I cannot see are the in-tank equipment that is outside of the picture.

The four Live components are excellent filtration and in fact, all that a reef aquarium needs to sustain itself. This is similar to what Mother Nature uses in the pond, the tide pool and indeed the entire earth. It's interesting and cool to find that the biofiltration grows to meet the needs, or in other words, the waste and pollution produced by pooping fish becomes food for all the algae, invertebrate animals, bugs, bacteria and worms in the aquarium. The more waste produced, the more the biofiltration expands to eat the pollution. It becomes a living ecosystem that can take care of itself and expand to meet the increased bio-load so long as the hobbyist does not change things too quickly, like adding too many new fish all at once. Does that make sense?

We have discovered unfortunately, from the many canister filters used by hobbyists that come to this MB, that a canister filter usually causes more problems than it solves, so it is okay, and even recommended, to remove it. (Break it down, clean it and let it dry.) If you choose to use it later, it can serve a useful purpose for running AC(Activated Carbon). That won't be needed for a while though.

In time as you gain more experience in the hobby, you may find that there are reefkeeping methods and tips of which the ordinary worker at the LFS is either not aware or does not share because their job is to sell you things. Just so you know, Damsels become very territorial and make life difficult for tank residents that come later. In the old days, one way to "Cycle" a reef aquarium was to add some Damsels and wait for 2 months before adding anything else. Damsels are pretty tough and either handle the water quality problems or die a sacrificial death to help "cycle" the aquarium. Perhaps you were instructed to use this method. No problem, you have already begun to learn a better way by adding Macroalgae. I see some LR and assume you have also acquired some LS from another tank, right?

It would be very helpful to see the entire tanks, so we can consider the placement and direction of the powerheads. Water movement is essential to a healthy reef. Also fyi, we have found that an open top is much healthier than a reef aquarium with a glass top. All of this and the further suggestions we might make, contributes to gas exchange. Good gas exchange makes sure that there is plenty of Oxygen in the water so that CO2 is kept to a minimum. This ratio of O2 to CO2 in the water, leads to proper pH.

Speaking of pH, it's actually not important to test pH and there is a good reason for my saying that. I can explain later. The reef aquarium's four most important water parameters are Temperature, Salinity, Alkalinity and Calcium. Would you mind sharing with us what these four readings are for your two tanks?

Mark

And the other powerheads. :)

Mark - We top off with ONLY RO water - will test the salinity of the pre-mix water I suppose.  I will then readjust the powerheads tomorrow morning.  We will continue to pull a gallon of water every day until we get the salinity down.  We were planning on a water change in the morning anyway - so we will run out to the LFS and get an alkalinity test tomorrow.  I will adjust the rockwork a bit tomorrow anyway and then will reposition the powerheads and discontinue the filter canisters on both tanks.  

Here is the maxijet:

Looking good.
In time, the Nitrate level should go further down, but at this point there isn't much need to test because the appearance of the coral will tell if something is out of line. The coral should start showing signs of growth. A good sand bed with fine sand on the very bottom and a variety of sand dwelling creatures like Amphipods, Copepods, Bristleworms, Spaghetti Worms, and Cerith Snails will help keep the N levels low.

The Alkalinity at 300ppm (17 dKH) is a little high. What have you been dosing that it went to that level?

I would remove the fan attachment on the Maxijet nozzle. It only slows down the water flow. Simply turn the pump just a little more (clockwise in that pic) and swivel the nozzle to get the water stream to hit the surface like this:



Edited by Mark Peterson - January 24 2012 at 9:11am