Ok, ladies and gentlemen, here's the outcome...
Last night I added 2 capfuls of Prime to the tank. This morning I tested the Nitrates and there was absolutely no change. I went ahead and performed a 20% wc. This included a thorough vacuum of the substrate, filter media rinsing, (in old tank water), and filter canister/intake tube cleaning, (ran under extremely hot water and rubbed down by hand).
After refilling my tank w/ fresh water, (treated w/ Prime), and replacing the Ich Attack meds I removed during the pwc, I decided to go ahead and add the Mopani driftwood. It has been soaking for well over a week, and was waterlogged, so I figured now would be a good time to add it to the tank. So far, yes, it's releasing tannins, but not a large amount.
The driftwood was added more for decorative purposes, but the pH lowering benefit is a bonus. I know my pH level is within normal range, and from what I hear, driftwood doesn't decrease the pH much anyway. However, I am more interested at keeping the pH level steady at a slightly lower level than they are now.
After waiting approx. 5 hours, I tested the water again. Here are the results from making a pwc and adding the driftwood...
pH - 7.6
Ammonia - .25
Nitrite - 0
Nitrate - 120
I say 120 for the Nitrates because the color wasn't quite as dark as it shows for 160, but it was slightly darker than 80. This leads me to believe that the pwc did help, but only a little.
It looks like I'll begin daily pwc's and see if I can get the high Nitrate level under control. I'm just hoping that this won't delay me killing off what Ich may still be lurking around in the tank. The only fish that still has white spots is the Neon Tetra that I believe was the one that spread the Ich to the other fish. Until his spots are completely gone, I'll continue treating the tank, but it's just frustrating because I've never had to battle an outbreak this long. Meh.
Anyway, the next pwc that I will perform will be 50%. I only did a 20% pwc today because my RT Shark was flashing pretty bad and I didn't want to put him under too much stress. The other fish, however, are doing great! They're no longer flashing against objects, and my Pleco isn't lethargic anymore. In fact, he's awfully feisty!
I guess, more than anything, I was hoping I could drop my Nitrates faster using an alternative method than doing large amounts of pwc's. But, that's how it goes. I normally perform 1 pwc a week and keep the gravel free of fish waste/food particles, so I can't quite understand how the Nitrate level got so high in the first place.
Even though this is the 2nd tank I've owned, I consider myself quite the novice when it comes to managing water parameters. I truly appreciate everyone's advice/guidance and welcome any additional suggestions/comments. Hopefully I will get my tank back to normal soon.
Thanks again!
P.S. Sorry for the novel.