Fun times this evening.  Having never really had to DO a formalin dip (counting my blessings many times over) I did NOT just willy nilly start off with the Maroons.  Heck no.  Instead, I started off with the Polymnus and Allardi.  “Practice” on the “replaceable” fish.  Now, they’ve been in a tank already being treated with Formalin at a rate of 1 drop per gallon.  Again, this is at hyposaline conditions of 1.010.
For the dip,  I went all around and found so much honestly confusing information, partially stemming from the fact that some forms of “Formalin” are the real deal (a 37% solution of Formaldehyde) and products on the shelf are DILUTED Formalin, but they really need to rework how they worded that and include a better description of the active ingredients in their products.  Why?  Well, because of course, being fried from OT, and thinking I’d really done all my homework, I went with the wrong concentrations in my dip.  Have probably killed my “replaceable” fish, having dipped them at far too high a concentration.  However, I was on hand the entire time and immediately removed them when I realized things were not going right.  An hour later, they are all still alive but clearly stressed, more so than when they went in.  “Smart Thinking” to practice, dumb thinking for reading the same manufacturer’s dosing information repurposed on a few websites and thinking “aha…OK, that’s straight from the manufacturer of this Formalin product, they call it Formalin…refer to it that way…I should be good”.   It was definitely MY FAULT, as of course, the formalin I own doesn’t have dosing instuctions for dipping, only for tank usage!  Figures.
OK.  I’m going to pretend I didn’t just do all that and go on again.  Oh, and that reminds me, when I did my hypo, I did check with my refractometer, but I ALSO checked the refractometer itself.  I don’t have calibration solution on hand (although I’ve made it in the past) but an easy test, checked it on RODI water, and then on my SPS reef (I don’t mix salt and test it anymore, I have a good volume based system that never fails me, hasn’t in all these years…).  Got 1.000 on the RODI, and 1.025 on the SPS tank.  Refractometer checks out OK by me!
Ok, back to the dips.  I’m about to go do them, and here’s what I’ve ascertained is the PROPER dip with REAL, true straight up standard FORMALIN.  1 ML Formalin per 1 gallon of water.  I’ll be pulling out 1 gallon of the hypo-saline water from the tank, adding heavy aeration and 1 ML (or 20 drops) of Formalin to the water.  The fish will remain in this dip for up to 45 minutes tonight.  I’m splitting the difference, as some recommendations are 30-45, others 45-60.  Frequency of dipping also varies greatly.  I have to pick SOMEONE’s advice, so I’m going with Matthew L. Wittenrich on this one – see page 161 of his “Complete Illustrated Breeder’s Guide to Marine Aquarium Fishes”.   3 dips, every other day (so tonight, Sunday night and Tuesday night), and we’ll see where we are at that point.
MANY others suggest that in addition to dipping, you need to keep a constant formalin bath going.  The logic is sound, given that you need to kill off the Brooklynella that’ s in the tank as well.  I’m fighting a tough battle on this one internally, and not every person recommends it, and it does some nasty things to the tank (i.e. it’ll definitely kill off the macro-life on the live rock).  In theory, the hyposalinity should already be controlling Brooklynella in the tank.  I haven’t made this decision yet.
While Formalin is universally cited as terribly nasty stuff (often as downright dangerous) it is widely considered the only really truly effective cure for Brooklynella.  What also sold me on going with Formalin is that it ALSO takes care of Amyloodinium (Velvet), which I have had tons of problems with in the past when it comes to Allardi.  Since this is the other likely disease to crop up, I’m killing two birds with one stone.  I need to also cite something I noticed, which is that Formalin can go bad and when it does go bad, it becomes more toxic.  Check your dates and for a white precipitation apparently…
I’m off to dip the FEMALE first with the new instructions I’ve outlined above.  Last fish to get a dip will be the Lightning Maroon.  Wish me luck, and send good vibes.  The fish certainly could use it.