Well, SE asked us to tell them which fishes we want the most, so here they are ;)
Freshwater:
- Ala Mhigan Fighting Fish
http://ff14angler.com/img/icon/f0031l.png- Discus
http://ff14angler.com/img/icon/f0105l.png- Paglth'an Discus
https://secure.xivdb.com/img/game_local/5/5007.jpg- Sundisc
https://secure.xivdb.com/img/game_local/5/5017.jpg- Marble Oscar
http://ff14angler.com/img/icon/f0350l.png- Bubble Eye
http://de.ff14angler.com/img/icon/f0339l.png- Dravanian Squeaker
http://ff14angler.com/img/icon/f0342l.png- Kissing Fish
http://ff14angler.com/img/icon/f0343l.png- Grip Killifish
http://ff14angler.com/img/icon/f0078l.png- Hotrod
http://ff14angler.com/img/icon/f0327l.png- Knifefish
https://secure.xivdb.com/img/game_local/4/4993.jpg- Root Skipper
http://ff14angler.com/img/icon/f0080l.png- Spotted Pleco
http://ff14angler.com/img/icon/f0073l.png
Seawater:
- Angelfish
https://secure.xivdb.com/img/game_local/4/4883.jpg- Lavender Remora
https://secure.xivdb.com/img/game_local/4/4901.jpg- Leafy Seadragon
https://secure.xivdb.com/img/game_local/4/4897.jpg- Balloonfish
http://ff14angler.com/img/icon/f0097l.png- Little Thalaos
http://ff14angler.com/img/icon/f0155l.png- Nepto Dragon
http://ff14angler.com/img/icon/f0290l.png
Another big wish would be a "ground" slot for the aquarium where we can put non-fish animals like the tiny axolotl, lake urchin, lamp marimo, ogre horn snail or mushroom crab, stuff like that^^
Also, just in general, I wish we could put the fish in the aquarium no matter which one it is as long as they use the same model (for example, Angelfish and Zalera share the same model, so if we own one of the two, we should be able to put it in :x).