Hi, we have a 60 litre with 6 danios and 6 Cory doras. We recently added 2 snails. We currently have gavel - however I now think the Corys and snails would prefer sand. Is this right? Can I scoop out some gravel and just put the sand on top, or is there a better way? The tank is around 3 months old so don’t want to upset anyone to much. Thanks!