At a lower level, if you manage to get crabatron by buying Shiny , is very good. He will eat the towers and render the cannons nearly ineffective ( because it is usually smarter to upgrade the cannons farther at a low level ). The disadvantage for using Crabatrons is that thy have low damage. They aren't as Ichis against monsters and towers without splash damage, but they can take splash damage better than Ichis. D.A.V.E.s actually has both a higher housing to damage ratio and housing to health ratio, so use D.A.V.E.s when you got them to level 6.
A crabatron has many tactical purposes.
1. One of them is the mob + splash diversion. Same thing as ichi, except this time the laser is involved in as well. Therefore, more crabs are needed to be hald back. The crabatrons wil be flung in together, preferrably at a point where they will go directly at a Cannon tower first. Ad they go on and destroy the towers, the threatening splash damage pops up, counter this by flinging in a zafreeti, but be carefull, you need to destroy the adt fast, as it poses a threat to the Zafreeti .
2. The Project X substitution method is a good method used between 35 - 40, where you send in your mob of crabs + a few PX's and a Zafreeti for faster takedowns. The problem with this is that the ADT tower poses a threat to the zafreeti, and if the zafreeti dies, then the Crabs and PXs will die soon. To try and counter this, try sending in your Fomor so it will buff your zafreeti making him last longer, he will aslo distract the ADT because, fomor is flying champ, so the ADT will fire at it too. ( Providing that your fomor is level 3 or higher ). if you don't have a fomor, you can try catapulting them, or using Putty to buff your Zafreeti .
Crabatron can be purchased with 14 shiny for your bunker
Putting Crabs in the Bunker is a good idea, because of their high health, they are able to hold monsters off for a moment, while other towers strike at them.It was also good for some Outposts