I have all five search coils designed for use with the Minelab CTX 3030, three Minelab coils and two Coiltek coils.
I also use all five search coils, depending on what I am searching for and the beach conditions.
The following are the ways I use my CTX 3030 search coils.
Minelab 6 inch coil
I use this hot little "Sniper" coil over coquina and coral outcrops, exposed on the lower beach at Florida beaches during extremely low tides or after beach erosion.
Tidal rock pools are another area I like to fish for goodies with the 6 incher.
This small 6 inch coil saves the need to carry a pin-pointer, detecting coins, jewelry or shipwreck artifacts trapped in holes of coquina and coral.
I also use the 6 inch in the water, searching cracks in coral ledges for jewelry and coins.
The type of areas other water hunters take a pass on because they are too difficult to search.
A small 6 inch coil can detect shallow targets close to iron obstacles that you can't even get close enough to detect using the 11 inch coil.
Coiltek 10 X 5 coil
The elliptical 10 X 5 is the bees knees at tourist type beaches, especially around trashy beach entrances.
I also use the 10 X 5 on iron infested beaches, as it allows you to get closer to iron obstacles on the beach.
No surprise, this coil is my go to CTX 3030 coil when beach hunting at trashy beach sites.
I often use the 10 X 5 when "Cherry picking" for gold in the dry sand.
Target separation is excellent using this coil and on eroded beaches you can sweep nearly the whole side of the search coil up against the face of the cut.
Reminds me of an 8 inch coil in depth and sensitivity to small targets.
Minelab 11 inch coil
I'm old school and believe the engineers who design metal detectors usually put the best all around search coil on a metal detector.
Saying that, you do need smaller and larger accessory search coils as the beach is forever changing.
As a good all around search coil the 11 inch will not disappoint.
I would say this search coil has the best combination of depth and sensitivity to a wide variety of targets at the beach.
This is the coil you should have on your CTX 3030 until you get used to your metal detector.
It's the coil I compare all other CTX 3030 coils to and a safe choice to travel with if your going on a detecting trip.
If your hooked on target ID readouts as many CTX 3030 users are, you get the most accurate in screen readouts using the 11 inch Minelab coil.
Coiltek 14 X 9 coil
I have spent hundreds of hours beach and water hunting with the newest CTX 3030 coil, it's a killer coil in the water.
Deeper than the 11 inch and just as sensitive in my opinion, but where it shines is in the surf.
My 14 X 9 has took a beating in brackish swamps, rough saltwater surf and on saltwater beaches with jagged rocks.
The tad extra weight over the other CTX 3030 coils is an advantage when water hunting, the 14 X 9 it's definitely not a floater.
If your strictly a beach hunter a detecting harness will help balance out the extra coil weight on the beach.
A nice "Tweener" size between the 11 and 17 inch coils from Minelab.
I run with an open screen (Pattern 2) in the water and wet sand at less trashy sites, maximizing the larger coil target depth.
Don't hunt by numbers as target ID readouts are not as accurate on deeper targets using large search coils
Minelab 17 inch coil
The CTX 3030 "Big daddy" allows you to cover serious sand at the beach. It is surprisingly sensitive for its size and target depth is not an issue.
I use this monster coil during sanded-in beach conditions when targets are few and far between.
Don't let the size fool you, it is surprisingly well balanced on the CTX 3030.
If you search rocky shorelines with decent size rocks, you can detect over the top of rocks with the 17 inch coil and still detect targets at decent depths.
I find Auto+3 the best sensitivity setting for using the 17 inch coil in the water.
If your using the big daddy it's probably at a clean beach, so run in Pattern 2 and lay off the CTX 3030 bells and whistles for improved target ID readouts.
In closing, you have plenty of search coil options for your CTX 3030, if you need another option.
My best advice is to only buy an extra search coil because it will help you detect what you are searching for in the places you search.
Different size coils can make a huge difference to a CTX 3030 user when you know why and how to use them.