One of my fish died last night .. is this the beginning of the end

[Twiglett]

all the others seem quite happy .. its been 11 days since they were put in the (uncycled) tank .. I've been changing 10% of water most days (although not for the last 2 days) .. and 50% of water every couple of days

I did change the filter day before yesterday ..was that a mistake?

twinset do your guppies eat the young? dh read that the guppies will breed but that nature will take its course as it were and that the young are unlikely to survive - oooh there are times I am glad I won't be able to see that.

they must eat some of them as they are continually reproducing and we are not overrun. But a fair few survive, so many in fact thatI am setting up a tank for someone else from the babies from my guppies and mollies.

I have a lot of places theycan hide though, my plants provide shelter at all levels in the tank and I have some fake grass that they love to hide in.

ah. although we have swordtails as well and I don't think the baby guppies will stand a chance against those.

I noticed the other week that our local fish shop has now got sachets of 'bacteria mix' in their fridge - can't remember what it was called, for short circuiting the cycling process. No idea if they work or not - haven't had the need to use one, but it should work on the same principle as adding a dirty filter.
And can second that guppies have an amazing ability to just die, when all else is healthy, ime the more fancy the guppy, the more likely it is. Partly why we moved on from them, plus the millions of babies.

Also watch that your sucky fish (is it yellow - Japanese sucking loach or similar?) isn't interfering with the guppies fins. We have lost a Columbian tetra to fin rot becuase it was being bullied and bitten at by our loach. Wouldn't have believed it if I hadn't watched it myself. (Culprit has now been segregated....) And I think that fin rot in guppies can be fatal pretty quickly.

And fwiw - though I have never heard of the daily water change process, i get the principle behind it, but i do think that changing the filter was a mistake - you need to be building up a stock of bacteria (as other have detailed) and the filter is where most of that will happen. At most for now I would just squeeze it out in some tank water to remove enough gunk for the water to flow through.
If you can get some testing kits (we use the little dip sticks that have mulitple tests) it will take the guesswork out of it.

[Chandra lets out a sigh of relief when knowing that sucky-fish is not in the list of fatalities]