Gravel change???

[Nico]

Friend of mine has a tank set up and running, however the gravel is unsuitable. (Glass beads, like marbles his fish can`t dig in them but keeps trying) It would be an easy job getting rid of them, but what about getting the new gravel in? I thought it would be pretty stressful on his fish (red devil)
Also, would it take out too much good bacteria and lead to amonia/nitrite spikes?

 

[Pufferpack]

Double post glitch

 

[Pufferpack]

Probably better if done in stages, move 3/4 of the marbles to one side of the tank and place new gravel in the vacant space. In a couple days take out another 1/4 and replace with gravel....should keep enough of the beneficial bacteria alive to prevent a mini-cycle