as above really, regarding more specifics of your last system.
But a couple of things stand out.
firstly the 'bugs' were probably copepods, which are good guys, and free food for your fish.
secondly the thing with a needle to measure salinity would have been a hydrometer, which are notoriously bad at being accurate. A refractometer (although a little bit more expensive) is a must.
Saltwater fishkeeping isn't really that difficult but as dave said it is impotant to regularly test (especially in the first few months).
Filtration is commonly done via the 'Berlin' method these days. which involves the use of circulation from powerheads and a good amount of live rock. with this method you have no need for filter pads etc. which tend to cause a build up of nitrates if not replaced regularly.
this forum has some really knowledgeable people on it that are always willing to help, so if you do decide to come back to the salty side we're all here to help. just keep the questions coming.
Rob
P.S. photos are a must i'm afraid!