My fish are hovering at the bottom of the tank

[Icetilly]

I added some sand and 1 piece of slate to my tank last Saturday and I noticed mainly the last couple of days my fish seem to be hovering at the bottom, what could be wrong, I done a 110 litre water change today and bought some API test kit which is nitrate 10 ammonia 0 nitrite 0, I didn’t know what PH to do so I did both low range 7.6 high range 7.4 any help would be appreciated

 

[fluttermoth]

Your tank looks quite empty, and severums are quite shy and appreciate cover. If you've changed from a darker substrate to a paler sand, that could have caused his behaviour; they feel exposed and are being as inconspicuous as possible.

You and I know there are no predators in your tank, but your fish don't!

If you can get some more tall or floating plants; even fake ones, and maybe cover some of the sand with dead leaves (buy Indian almond leaves, if you're not 100% sure about collecting your own), that would make them feel much safer, and they'll be happier to come out and about more