What would happen if you put more than one alka seltzer tablet in a lava lamp?

Putting more than one Alka Seltzer tablet in a lava lamp can cause the liquid to bubble rapidly and overflow, creating a mess. It can also potentially damage the lava lamp by putting too much pressure on the glass and heating element. It is not recommended to use more than one Alka Seltzer tablet at a time in a lava lamp.