Fish I Acquired When I Purchased A 2nd Hand Tank

6 of these

5 of these

Think I've identified  this as Black Tetra

Thanks

I had no idea that black skirt/widows faded like that with age.

That sounds like me as well 

I'm struggling to keep up with what fish you have / don't have.  You don't mention the platies here, I thought the guppies were borrowed for fish-in cycling, and I thought the penguin and cardinal tetras were your friend's.

For your Fluval Flex 123L's footprint of 82x40cm footprint, the species of fish you have mentioned are fine for the tank size [NB actual numbers of each will be mentioned later]:
* the black tetra, platies, guppies, penguin tetra and bronze cories are fine for your water hardness of 207.75 CaCO3/ppm or 11.64 German degrees hardness;
* the neon tetra and cardinal tetra would be just about ok for your water hardness (but might struggle);
* see Sue's point about the substrate for cories.

Please confirm how many fish you have of each type, and if there are any more that haven't been mentioned, then we can either advise accordingly - or it would be good to familiarise yourself with https://www.thinkfish.co.uk/article/community-creator to work this out for youself. It sounds a lot of fish already, though, for the tank size!

Presumably you're keeping the 57L Fluval Flex as a hospital tank for fish if/when any fall ill and need isolated for medication treatment?

I believe my 57 is cycled now in 5th week. I have no Ammonia no nitrite and Nitrates at 20ppm. I did it all wrong with fish being new to fish keeping but kept on top of it and not lost any fish in the process.

It is always best to give us full and upfront/honest details at the outset, as it makes it much easier for us to help you. For example:
* on 31 Aug, you mentioned the tank was cycled, and talked on 9 Sept about plans for potential stocking when the tank would be at the stage of being ready for fish, then told us a couple of days later that you had been using friends' guppies for cycling for the previous few weeks.  Now it seems there were also penguin tetras and cardinals in the 57L, possibly going through the fish-in cycle along with the platies or guppies.  If we had known all of this at the outset, we could have helped you through the fish-in cycling process based on the history of your daily readings for ammonia/nitrate/nitrite and when any water changes were done, and we would be in a better position to advise on whether or not the 57L tank is cycled or not.
* Also, had we known this, we could have assisted you in advising on a suitable-sized tank for the stock you had (possibly a Fluval Roma 240L) and an appropriate substrate, where to look for one, etc, without you finding yourself with additional fish that came with the 123L ie black widow/skirt tetras, neon tetras and cories, and now in this difficult predicament of having far too many fish for your tank(s) to cope with.

If you're keen to keep all the stock you have, then I'd advise looking at additional tanks such as the one I mention above - but please resist the temptation of purchasing one that comes with even more fish! 

I am sorry that you have not been happy with my/our efforts to help.  I can assure you wholeheartedly that I was not “backtracking your posts to try to catch you out” – instead, I was doing my best to help you all along with the information that you had provided, as have others also done their best in response to your previous and other posts.  This necessitated going back through your posts to try to re-establish the various points, as there was so much conflicting information that it was difficult to figure out how to help.  When someone asks questions on the forum, others build up a sense of their set-up and are always thinking of what sort of advice might be helpful.  On a number of occasions in your case, additional information has suddenly been provided which has made best efforts to help and provide suitable advice extra difficult – more fish in the equation that we hadn’t been aware of, etc.  I apologise if my exasperation at this came across – the point that I was attempting to make, and which I’d encourage any fishkeeper using this forum to make, is to:
* give us the full information from the outset (eg cycling method, stock or proposed stock, tank size), etc.;
* keep us updated as they go along such as any intentions for stocking, discuss alternatives/options, etc, rather than ask for advice, then advise us after the event that actually more have been acquired and a tank of a certain size purchased, which then makes efforts to help you even more difficult – eg we could have advised not to buy the penguins and cardinals if you had already got the 123L with fish, or vice versa, or advised on a suitable sized tank or number of tanks of what sizes in the circumstances.

The internet is full of information via video and print from self-described “experts” which anyone could call themselves, staff in shops are trained to sound very knowledgeable, and there is huge variation in quality of this advice from downright appalling (yet which sounds plausible) to excellent. It can indeed be very difficult for a newcomer to know what the quality of that information is, and who to trust, to decipher the poor from the good quality information. However, sources such as www.fishbase.org and www.seriouslyfish.com are very reputable internationally with regards to species’ requirements – the latter is a more comprehensive and up-to-date source than the good, helpful and user-friendly Fish Profiles on here.  This is where many of our responses re each species’ requirements are derived from, as we at Thinkfish prefer to provide advice from good quality sources renowned internationally on the basis of collective fishkeepers’ experiences (in addition to referring to our own experiences where applicable – and will specify where this is the case) than try to sound like an expert based purely on our own experience.  I hope this explanation is helpful.

[Dictated via voice-activated typing – hope it is coherent.]