Well i'm sorry to say this but if you keep buying fish and adding them to this tank BEFORE it is completely cycled or cycled along far enough to even support life then you will be spending ALOT of money on fish. Your best bet is to be PATIENT like I stated before. Keeping SW fish isn’t like keeping Gold Fish. SW fish are more delicate than Gold Fish. Water qualities in most cases need to be pristine.
Yes remove the dead fish. If not then you will get a lot of bacteria you DONT want.
Also about the power head...any form of current can move sand. You want around 10X the turn over rate for the amount of water. So if you have a 10gallon tank that means you need to have 100 gallons of water being turned. One power head will not be sufficient in a SW aquarium. One power head will create dead spots in your tank for ditrius and other nutrients and such to settle down at creating a feeding point for un-wanted Algae’s.
Your PH is a big worry. The Typical Surface Ocean Value of Ph is 8.0-8.3 (can be lower or higher in lagoons). Also if you can post your other parameters that would be more helpful, Low doesn’t help us much. As for water quality your goal is this:
Ammonia - less than 0.1 ppm
NitrITE - typically below 0.0001 ppm
NitrATE - typically below 0.1 ppm
Calcium - 380-450 ppm Typical Surface Ocean Value is 420 ppm
PH - 8.0-8.3
Salinity - 1.025-1.027
I hope this helps and I hope that you take heed in the idea of being Patient.
