Think Fish Keepers Daily News. [2016-2019]

Thanks guys. 

As far as water goes, if you do regular large weekly water changes on both tanks there will be little difference in the water - unless you do something in one tank to change the water such as adding calcareous rocks to one of the tanks. In this case, then yes, add some main tank water to the QT for a few days.
But as far as 'bugs' are concerned, swapping water will do the same as moving the new fish over without doing that.

Good to hear that your gang were all fine during your absence.
I hope that your rasboras acclimatise quickly tomorrow morning, and enjoy the main tank. 

Thanks, @Littlefish.

@Matt, if I work out my stocking based on eye judgement on size, I have:
* 3 tetras at 4cm each = 12cm
* 6 harlequins, 4 at 4cm each, 2 at 3cm each = 22cm
* 6 neon greens, 4 at 3cm each, 2 at 2cm each = 16cm
Therefore, I'm increasing my stocking by 47% (or less, if we count the snails, one of which poos its weight daily due to spending its time grazing on the bogwood).

I am keeping my eye on the two smallest neon greens - although all came to greet me and all eat, one seems to be spending a lot of time on the bottom rather than swimming with the other 5, and the other small neon green occasionally drifts off to spend time on its own at the side. There's also the cloudy-eyed male tetra whose cloudy eye looks as though it may benefit from treatment. Depending on what the situation is in the morning, It might be that I keep some media in the QT and treat 2 or 3 of these 3.

Now down to just 1 of the harlies harassing the green neons - Alpha Harley seems to have spent the entire day chasing one after the other of the green neons (except for no.6 who has spent the entire day down on the substrate - not convinced about the welfare of this little one, and the one with the missing portions of caudal fin who was understandably hiding in plants but seems to have vanished altogether).

I like watching a tank when different species are getting used to each other.
I hope that the neons are settling, and that the ones that are hiding come out tomorrow. 

Hopefully number 5 will gain some confidence, and spend more time out in the open with the others.
Things don't seem so positive with number 6 though, which is a massive shame.

I agree with your filter process. I would do a third or half of the media at a time, and wait for a week of positive test results.

To be honest I would replace them from a numbers point of view, but I also wouldn't add them in after the others get settled because they would have to establish hierarchies all over again. If it was me I would add more now without quarantine... especially given you know they have been ok in the shop, but I understand you/others may be more hesitant to do this than me... 

That wasn't pleasant. Went to retrieve the fish from the bottom of the tank - he started moving slightly but willingly went into the net. Breathing was rapid and he was lying on his side while in a small container.  Having almost done the deed before nature took its course while I was plucking up the courage last month, I did it this time for the first time in my life. He moved slightly with the first few drops of emulsified clove oil, then death was instantaneous with the next few drops. Vodka has been administered to complete the process once certain that he was well-and-truly gone. Quite shaken, really, but at least it avoided any more of a prolonged suffering for him.
 

There are times when it is more cruel to let a fish live in obvious pain. You did the right thing.