Oh no, I'm sorry.
I know you don't want condolences because of the guilt, but it's because I know you'll be feeling horrible about it, and I know that there isn't a fishkeeping in history who hasn't killed a fish through one mistake or another. I know I have, cried tears over it, felt awful - and learned lessons when it did happen.
I'll give you a real example where I killed some fish. I'm sure I've mentioned it on the forums before as an example in cases like this. So early into my time in the hobby, I'd been breeding guppies for a little while, doing the thing where you try to save and count each batch of fry, and was very attached to my group of six lovely females who were popping out fry like the Millions Fish they were.
But I'd reached the point where I'd got a bit overconfident and relaxed as the numbers got overwhelming and my attention was divided among more tanks. Noticed the sponge covering the intake on the small canister filter I had had a split down the side, so I rubber banded it on tight and pressed the split part against the back glass. Impressed myself with my thrifty and quick thinking solution, I didn't make a note to order or pick up a replacement sponge, and kept forgetting.
Then maybe 2-3 weeks later it was filter cleaning day, I opened it to find a load of guppy fry inside the canister. Panicked, felt awful - some were alive and seemingly well, and I rushed to scoop them all back into the main tank. But several had died, and some had survived, but been injured, and passed away soon after from their injuries/secondary fungal infections. Of course at some point while doing tank maintence or netting fish or something, I'd knocked the filter intake, the split part of the sponge had shifted and opened just enough to let a good amount of guppy fry get sucked through the pipes and into the filter. I hadn't noticed, hadn't replaced the sponge straight away, and since there were so many guppy fry in that tank with the adult females, I hadn't noticed that 20 or so had vanished. So I felt awful. My mistakes and laziness/lack of urgency had killed some of my baby fish.
But we're only human, human error is a thing, and you learn lessons each time. There are also a lot of people in some areas of the hobby who love to jump all over anyone who makes a mistake, even if it's a true accident, human error, and they already feel badly about it! And that always bothers me, because I'm convinced they've all made mistakes too. Just won't admit it publicly.
One thing no one can doubt is your love for, dedication to, and willingness to go above and beyond for your fish. This whole thread is a testament to that!
So I do want you to process your natural feelings of guilt and grief, by all means, but to not beat yourself up over it for too long... okay?
Also don't forget that the brain plays tricks when we do things that are routine to us, but ever so slightly different. That often makes us forget steps that we'd usually make on autopilot, and because you usually do it so routinely, but the routine is off this time, the brain just... skips. Like a vinyl record. Horrible example to use, but one that can explain the brain processing better, is the cases of babies left in hot cars by accident. The research seems to show that it happens most frequently when the routine has been changed last minute. Say a parent who doesn't usually take the kid to daycare, but has to one day as the usual parent can't. So they strap the kid in the car planning to drop them at daycare on the way to work, but as they drive to work daily, the brain goes on autopilot, since this is a task and routine it does daily, usual thoughts about planning your workday, what you're going to make for dinner etc kick in, and they autopilot drive to work. Kid has fallen asleep or is quiet in the back, parent does usual routine of grabbing bag/keys/wallet and heads into work, forgetting all about the kid in the back.
Sure, it can happen in negligence/potential homicide cases too, but it's been frequently seen enough for the patterns to have emerged, and fits with a lot of what we know about memory processing, and how routines and habits don't require our full, undivided brain power, and the brain will conserve energy and focus attention on other matters. Anyhow, sorry for the grim example, but they're doing things like adding a "check the backseat" thing to some cars now, and there are tips like putting some essential item in the back when you have your kid in the car, as a way to prompt you into a new routine of checking the backseat each time.
I suspect something like that is how you forgot the declorinator. Yes you declorinate each time, but you were only using a small container this time, likely thinking ahead to the other parts of it, and because declorinator is usually such an automatic process for you when it comes to tank stuff, your brain was like "routine detail, SKIP! Focus on new thing we're about to do". Which is why it's the one basic you always do, that was so easily forgotten this time around. It just sucks that it was the time it was a small container and not enough water volume to dilute the chlorine. I'm sorry.
My group is now down to five fish. I don't yet know if it's worth replacing the two I killed, since I suspect I'll have to rehome the remaining fish anyway, when I move in about a year. I'll think about it.
Edit: I'm actually already leaning towards getting more. The tank just doesn't look right, and I'm finding that the small number is stressing me out. Five neons might as well be one neon.
I'm really glad you changed your mind in the edit!
A year is a long time, and the first thought was more likely because you feel awful about it. A year is a long time, you've been loving this hobby and doing well. It's a sad setback, but an honest mistake.
I've heard several times now that neons are generally getting weaker - and we do see health issues crop up in them a lot here... I know this wasn't the result of anything like that, but I've also been thinking about the conversations in the fish TB thread, and whether the general weakened state of neons, that used to be considered really hardy, essential in every community tank kind of fish. But
@GaryE @Colin_T have you guys also noticed/heard about general consensus of neons not being very healthy fish anymore? Might be unconnected to fish TB - I'm sure I've also read opinions that it's because they've been mass farmed for so long due to demand, and it might have weakened the genetics/general stock?
And I mention that before you replace with more neons, in case you decide you want to try another species with the ones you have left, rather than replacing with neons just because you already have neons, you know? For example, cardinals are usually still regarded as hardier than neons now I think - personally, I prefer their looks and swimming motions - but they'll happily pal around and swim with the neons too. So you could bump up the numbers that way.
When I inherited dad's tank, it came with the last few remaining elderly tetra from larger schools he'd had, so I had an odd mix of a few of each tetra species, like a pick n' mix of one cardinal, a black neon, three glowlight tetra (the real glowlight tetra, not the neon DNA altered ones), just two bronze cories, etc. I got more cories to keep the two company since I planned to keep cories myself, but I didn't want to bump the school numbers of those tetra species, since I didn't want to be stuck keeping those species forever myself, just for the sake of keeping the numbers up, since that would never end.
Byron was super helpful there. Pointed out that letting these elderly tetra remain in the tank they'd always been in, with other fish they'd lived with for years of different species, was kinder than buying a load of juveniles of a species I didn't want, to add the wrong sort of water. And rehoming a single elderly cardinal to someone with an existing group, even if I found someone who'd agree to take it, might be much more stressful for the elderly fish that's suddenly been added to a school of youngsters that might pick on it, as well as the stress of the move and new environment. And the remaining tetras did pal around together, for the most part!
So if there are other species you've thought you might want to keep that would work in your tank and with neons, it would be worth considering now whether you want to just bump the neon school up, or if you'd like to add another variety. Since the tank is more established too, you might be able to bump the number of neons, and add a school of something else, perhaps.
