So here is my assessment and I always defer fish disease advise to the experts here who have responded to your thread.
You have a 6 month old 70g DT. This is actually 50g with rocks. You had a hippo tang in there which should have never been in a small tank like yours and then you recently introduced the SF tang which also should not be in a small tank like yours. Both fish would be under significant stress due to conditions and then you combine the power outage with equipment glitches such as RODI over fill and you begin to have a recipe for failure. If the new fish did bring disease in then the stress of the environment caused your fish immune systems to fail quickly resulting in fast death. Once the big fish succumbed then the small fish were quick to follow. So disease is certainly a probable factor but there are also other contributing factors.
You seem to have a lot of nice equipment for your tank why not a battery back up also so power glitches don't nuke the tank? You posted your parameters but you also mention battles with dinos and now bryposis (sure its not normal GHA?) so your parameters are not good but in a 6 month tank this is to be expected. Dinos can release toxins and sometimes cause harm to fish. This may have also added to the stress in the tank. You mention a dead fish clogged up your downpipe which may have caused disruptions to normal filtration levels also. This of course can lead to other problems if the water is not being filtered properly and fish are under stress. There could have been an ammonia spike from a dead fish that cased a chain reaction with the other fish also. The 3 suicide volunteers you added to the tank died very fast. This leans more towards tank environment and water chemistry with toxins, stray voltage, lack of proper filtration resulting in 02 issues, etc... but you still can not rule out disease here either
It is hard to say definitively what caused your issues but it appears to have been somehow connected to the power outage and this stresser may have triggered other problems in the tank for the fish. Best course is to fallow for 60 days, do regular weekly water changes, work on your nuisance algae issues, check all equipment for function, make sure flow is adequate with good surface ripple for gas exchange, add ammonia to keep your cycle going, build your biome even if just a few small pieces of real live ocean rock, see if any pollutants with ICP tests, then introduce a properly QT fish or 2 back into your system and see how they do for a month.
Dont introduce harsh chemicals into your tank to deal with nuisance algae unless it is an absolute last resort. You will open the door for a host of other problems by doing so. a 6 month tank is barely developing its biome and for another 6 months will be unstable and unpredictable so just add basic easy to keep corals and fish that are appropriate for your size of tank. I have a 65g DT with 12 small but very colorful fish. I experienced disease and fish loss to when my tank was brand new and had to fallow as well. My tank went through ups and downs the first year but then became much more table and predictable so my corals and fish thrive now.
Take your time.
thanks. yeah i do have a battery back up on my two gyres and as far as flow i also have two wav pumps. i had been gathering all the equipment 6 months before i filled the tank. which is why i was able to research and plan my sump area to the best of my abilities.
sailfin i knew was going to get big and would trade it in at that time. same with the hippo, the hippo when i got him was smaller than the chromis and always schooled with the chromis. it was kinda funny. all the fish were coexisting happily so i didnt think it was aggression stress. sailfin didnt even get out of the acclimation box when this all went down.
the dinos im pretty sure are dinos and not algea because they disappear at night. been dosing phosphates to help that front and not adding any chemical like dinox. i know these are temporary bandaids dont fix anything and only kicks the can down the road.
the bryopsis started popping up a few weeks ago. not sure where it came from exactly. ive been dipping all my corals and dripping (usually dipping) my fish. maybe some survived the dip or spores that were deep in the marco rock.
the only treatment that ive read and talked to other people about the bryopsis is fluxrx and was told its reef safe with the exception of any macro algea in a refugium which ill pull mine out. im not one to use a type of algecide because its a band aid but i haven't seen any other sure fire method for bryopsis.
i did check ammonia the first day it happened, it was still zero. but you mentioned adding ammonia to keep my cycle going but my tank have live animals still which are doing fine at this point.
im not trying to say ive done everything perfect but i know cycling and the time it takes and testing. i expect the ups and down and been dealing with that. i just didnt expect a 12 hour span would wipe them when everyone was getting along and thought i had been doing a decent job with equipment and acclimation. could have all the factors together at the same time caused a melt down? yes. but it wasnt like im dumping a mandarin into a 1 month old tank.
ill be waiting for an icp test as well as fallowing. i didnt want to initially spend 50$ on a test when people thought it was velvet which icp wouldnt catch. at this point i will continue my weekly 12% water changes until i get the test back.(not sure how long they take) if its a toxin on the test or not, i will still do a series of massive water changes, add my phosphates back in after stripping what i had, feed a little bit of food for nitrates, and start bryopsis treatment. at least with an icp test i can rule out a heavy metal toxin.
At this early stage, why not just do a rip clean and start from scratch? Rehome the inverts back to your LFS, and corals if you have any yet. Ensures no more disease, and if there’s a toxin or contaminate that doesn’t show up on a ICP, it’s gone too. And toss that 3D printed thing and use one that won’t leach chemicals at any level or age. Just my 2 cents.
i will get petg filliment in about a month and reprint the guard on my cor20. since i haven't had snails get down inside my sump yet, i think its safe to take it off for now. pumps are expensive and just dont like the idea not having some kind of guard on it.
as far as resetting and rehoming, i have put alot of work into this tank thus far and i will at least wait for icp test and fallow to rule something and then go from there. this would be a last resort option for me. i already have corals growing and dont want to stress them further by rehoming them after they've acclimated to my tanks light, flow, and schedule.
