So I’m buying an already established tank and saving all the water during transportation the guy is keeping the fish but giving me the live rock sand etc my biggest question is right now is what type of fish would be good for a beginner and how many I should be getting I come from fresh water experience especially planted tanks with guppies so over population happens a lot because of how fast they breed lol so I really am not sure on this any help and answers are welcome want to add that the tank is a 29g biocube with upgraded lighting and filtration but I’m not 100% sure on brands as of right now