The magma tower is basically a downgraded version of a tesla tower, so treat it like a tesla, except with lower range. Protect it with long range towers, or upgrade it to the maximum level to avoid Rocket DAVEs destroying it. Putting it beside the Quake tower makes it very powerful.
Just like the tesla, except with fewer monsters, then you can take it out much easier. Unfortunately, this tower does not take a huge amount of time reloading, so it is best to keep on sending monsters instead of trying to wait for it to reload (as the tesla does)