FYI, my system didn't crash. ;)
Zero nitrates will not crash your tank.
In my case, my REFUGIUM crashed. I had a literal 12g solid brick of cheato that could hold up a jug of apple juice.
But silly me let the nutrients drop to nothing, for too long and this caused the macros to start dying off and it wouldn't stop.
This seemed to throw everything off balance and dump tons of micro nutrients into the tank and it was a downhill spiral from there, especially with Triton dosing more micro nutrients into the tank to feed the refugium, which would no longer support any macros. Treating with chemicals for the resulting dinos wreaked havoc on the system too. So I CHOSE to cut my losses and start fresh since the tank was young anyway.
But that said, coral need food. So it's good to keep a few ppm of nitrate in the tank.
And don't forget p04 either.
Systems like Zeo will let you keep ULNS but IMO the tank is always on the brink. One false move and boom.
OK, now that I re-read your posts, I realized that you
*chose* to take down the tank. I initially glanced at the pictures (just like a kid, picture stories are fun! ;)) and assumed that your whole system crashed, but now it makes why you had corals left, because you chose to take it down and start over again because of the dinos, which I didn't know were a problem until I re-read the story.
Makes sense now, because that would have been a really frightening thing had your system crashed due to 0 NO3. Technically, you could have reset the refugium and without the dino problem been fine I am guessing? I saw the video of how thick the chaeto was also; that is amazing you had that much! My apologies for bringing you into this post with an assumption that was incorrect D2. My apologies also for not reading thoroughly enough to understand why I saw a picture of an empty tank. :confused::confused::confused:
To help the OP, in your opinion, 0 NO3 is not necessarily going to do any damage, but more like walking a tightrope. My apologies to potatocouch for using an analogy that doesn't work, in this case, the D2 story. Man, I'm full of apologies on this one, got every angle wrong.
Thanks for the update and advice D2. And I maintain my original perspective on keeping NO3 levels detectable. 5 ppm NO3 isn't that high and will really help the corals grow tissues, since they need the nitrogen content in building amino acids to build proteins.
On that note, I think I've done enough damage. :eek::eek::eek:
Good luck potatocouch! I'll follow to see others advice; I don't run an ULNS, I keep NO3 between 25 and 50 so I don't have to worry about getting to zero. Everything grows really well with those levels, and no algae.