Adding Live Sand to an Established tank

[Oscar]

When I first set up my nano tank a few years ago I started with 1-3" of live sand which I think was Caribsea Arag-Alive.

But after numerous vacuums and probably some dissolving it is time to add some more sand. The fine particles (<1mm) of the current sand is a real collector of detritus.

I have purchased a small bag of Carib crushed coral substrate which is listed as 2-5 mm. At this stage I am not sure if I will gradually do a "swap" of fine sand for coarser material or just slowly add and mix the two together. I will have to consider this in context of creatures I want to add in the future.

I am proposing to add this gradually to the tank, perhaps a couple of cups per day. Since it is not inoculated with bacteria I will dig a hole to add this to, so as not to bury the existing sand.

Any thoughts on adding / changing sand?