I don't mix assassins and other snails, but I have seen assassins on a nerite snail in the absence of other food...I think it possibly comes down to whether you feed the assassins once they have run out of the pest snails you are presumably employing them to eat...if they have easier food then they might not touch the bigger snails.

I would move the apple snail if it was me. The assassins would go for the easier prey first and then chances are they would turn on the bigger snail if they were hungry.

Kittycat, if he is sniffing the food and swimming off it's possible that he doesn't recognise it as food. If he has never been fed peas before he might not realise how delicious they are. Of course, he could be off his food because of poor health and I would always assume the worse, but just making a suggestion.

You're doing the right thing with getting him a bigger water volume..I would be doing 50% changes a day though just to be safe until you get a test kit so you know what state the water is in. You can get them in the LFS, or they are a fair bit cheaper online....if yo can get the liquid test kits rather than the papaer strip kits that would be better as they are more accurate.
Good luck with him :)

Hi Viriconia,
I would take them off his hands and put them in the 110l for now.
Unless you can upgrade it won't be enough long term....but you can always then find a shop to take them, which is what you suggested the bloke did.
Giving them to an lfs may not be the most ideal thing, but it's better than being flushed.

With your nitrate test, try banging the bottle a few times on a table before yo do all the shaking. The contents of the bottle can get stuck and not mix properly and if this happens then the reading will be wrong.

Have you used any medication recently that could have affected the bacteria?

Did you do a nitrate test?..some fish can be sensitive to changes and as you've added an extra fish your bioload will be higher, meaning more nitrate.

Kelly, your tank sounds amazing..such a lovely size.
In your OP you said that your nitrates rose and then fell...did you mean nitrItes? Nitrate shouldn't be falling during a cycle..you want it to climb as it shows that the cycle is progressing.
Great news that your ammonia as dropping to zero so quickly, is your nitrite doing the same thing?
And my opinion on your how to introduce them query..for me it would depend what ppm you have cycled to. If you have been adding a lot of ammonia then the 2 fish should be fine to go in together, but if you haven't been adding a lot of ammonia then add the fish one by one.
Good luck with it