It will dissolve but not fast. So I have no way of knowing if it will be enough for your tank. I however have a sea shell in my filter and it sonly there to prevent my water from going acidic. I get about a year out of one one before I have to add a second. its' great for keeping the PH stable but as a source of Calcium for plants it is not the best solution.
The big advantage of a GH boosters that you get calcium and magneium at a known ratio. The problem with coral and sea shellsisthat it is mostly calcium and may not have much if any magnesium. So with coral or sea shells it is still possible to run out of Magnesium. If you follow the directions of GH booster bottle and only add a enough to increase your GH by 2 degrees harness you hsould have enough calcium andmagneisum without doing any harm. Also get a GH test kit. That way you can determine how hard or soft your tap water actaally is. And you can use it to verify your are dosing correctly. In my opinion the risk of overdosing is very low.
