I took care of the water and fish..in all types FW, brackish and SW. Worked behind the wall so to speak. Water changes, making new RO/DI and SW to be sold and for our systems, feed, cleaned tank, removed anything that died, acclimated new stuffs(tuesday always my fav)...water tested tested and did more testings. Customer had a Q about water did more testing... Dosed meds(back then it was mostly just dump copper in) Did help build a new wall of tanks was interesting learning the plumbings. I did talk to customers...but wasnt considered sales....more if the sales didnt know I try to help. Bagged fish when sales were busy, bagged blood worms all the time as sales thought(it was like one chick) thought they were disgusting.
(I fell in love with SW b/c of this job and puffers OMG puffers! Brackish ones too! best way to get to know fish personalities. )
BUT the above idea might be right too.... if they have a home maintenance service. Which doesnt sound bad to me as a summer job..go see and play with really rich peoples tanks and fishes!
Pay I got .50 cents over min wage back then. I would expect it to be around about that today, not going to be a high salary thing.
If you want this job you need to be proactive about it.
Give it a day or two then go in....Make sure the owner/manager got your application. Make sure they know you know tanks.(assuming you know tanks...go learn some tank stuff right now if you dont lol) Not many people ...let alone young willing to work starter jobs know what the cycle is. (which will be the #1 issue dealing with customers :facepalm

Make sure they know your excited about this, that you are serious about wanting to do a good job in this.