Garden centres sell pea gravel, often golden, a mix really, in subdued colours, 1-3 mm for about £10 for 25kg, works a treat, you do need to rinse it with a decent kitchen sieve under the tap first. More expensive alternatives are available. The goldfish really don't care, they love mouthing pea gravel, in fact with good filtration, hornwort growing above them, and regular feeds, goldfish are ever so content with life and very long lived and very quickly in my experience, hand tame and aware of routines. I had goldfish in a good sized tank in my kitchen for some time, quite miss them now, they are in the pond, they got ever so excited when I put the coffee on in the morning.
Yes, absolutely, they love silver sand/playpit sand, endlessly passing it out their gills after nose diving into the surface, under the microscope, sand - I don't have a microscope, I did a quick Google image search after your post got me thinking - looks like lots of little pebbles/cobbles, hardly completely 'rounded' but certainly not sharp and jagged. A bit like 'sea glass', which I suppose should not surprise us. Goldfish in my experience don't mind horticultural grit, but they don't quite mouth it, they sort of pick it up and spray it out. All good fun I suppose if you are a fish. Biofilm and mulm are I suppose actually quite tasty for fish.
I’ll have to try and get a sample of that for my next tank. It’s quite light in colour isn’t it?
Yes it is quite light in colour but worked well for me 👍
