[Mike Mazur]

as big as you can afford and be creative with this part go for the biuggest liner you can get and hope you do it big enough the first time around. liner is the biggest hassle to deal with later. you can always upgrade filtration and circulation as your fish grow min size and number. landscape can be put off as well. fo shape it needs to either fit and look natural or depending on style of landscape it can be formal. as far as shape stay away from sharp corners. they cause areas of poor water movement and stress for liner. concrete doesnt care as long as it is reinforced of course. flow through or circulating depends on constrictions to that much water use and a source for water and the waste water. waste water does a nice job for watering the landscape. A jet pump cam be plumbed to the outlet and plumbed to the irrigation system and there ya go water for the lawn. keeping in mind the salt level you choose to run makes this a go or no go. otherwise Steep sides and a sloped bottom to the drains. circulation can be acheived many way through jets is one way I let my waterfall do the job. as it enters the pond it comes in along one edge and gently rotates around the perimeter a full 90% untill it is picked up by skimmer and a far end botom drain.

As to which is best? opinion and experience with your setup and your fish and your method of keeping play a large role.