It's hygienic to do but for the sake of the fish the tank will need a weekly water change.
I would urge you to get cold water rather than marine or tropical because it's much lower maintenance
Actually tropical fish are far easier to keep than cold water fish.
The trick is a decent pump system.
Goldfish are seen to be the easiest fish to keep but they are the biggest poop producers ever.
I've kept both tropical and cold water fish for years.
I'd say go for tropical, as has been mentioned guppies, barbs and danios are fab. As are neons.
Ask at the fish centre how many of each fish your tank can hold and stick with their recommended numbers (and at least 5 for their own group or they'll be bullied) but add a plec and a handful of amano glass shrimp too for tank floor maintenance.
Remember a tank should be completely set up for about a month before adding fish, the shrimp are hardy so they can go in right away plus they start the cycle of levels.
A top tip, when you clean the filter do it in water from the tank (in a separate pail) as this has the natural flora and you don't want to wash it away with tap water high in chemicals not meant for fish.
Do 10% water exchange weekly.
Trim natural plants back as they could stop the light getting to the bottom of the tank causing dank areas.
Don't have near sunlight, this causes algae.
Be wary of sand with a plec as it can scratch their soft under skin.
The fish will breed and natural selection will keep your tank down... The fry will be lunch for many!
OK I'm being a fish tank bore now, I've a big one in my living room and going to set one up in my beauty room too