[Jimbo327]

Here is the lesson you need to learn from this.

1) Go Slow (adding bioload and making any changes)
2) Do not medicate your tank unless it is last resort (might want to use a q-tank when using any antibiotics, certain antibiotics will help some fish but nuke inverts) When your fish looks sick, it is a sign that your water quality sucks and they are stressed, but usually corals react much faster than fish.
3) Use common sense, and double check your testings if something doesn't fit logically (if you change your substrate and get zero nitrates, don't you think something might be wrong?)
4) Actively run carbon after any type of medication is finished. And make sure medication is completely reef safe.
5) Keep your tank stable (once you detect a wipe, ammonia & nitrite, then you need to react quickly by running carbon and doing a series of water changes...best to keep the lights off as well)
6) Do not change your "working" system because someone says something is a nitrate trap. (Look, there are so many ways to run a saltwater reef tank, I've seen beautiful mature 5+ years SPS tank running CC). But if you want to make a change, go to step 1 again.

Consider yourself lucky it is a small tank, I've seen wipes on large tanks, and it is ugly and very expensive.

At this point, don't get too down on yourself, you need to check what is in that medication and if it is reefsafe. If the medication is reefsafe, ie not contain copper or other nasties, then you can run carbon and do a series of water change over a couple days to get the tank stable again. Then you gotta wait until your levels are low again for several days. One low reading doesn't mean much because of the different stages of the nitrogen cycle. Once it has cycled again, then you can start adding bioload slowly.

If the medication is NOT reefsafe, then you need to basically throw away all the LR and sand in the tank and scrub that tank, and start all over with new pieces because you don't want the medication leeching back out of the LR/substrate and killing more stuff.