"Aquarium" cards are the true strength behind "Aquaactress" archetype. The three current "Aquarium" cards give them attack boosts, immunity to monster effects and double ATK when they battle, while the "Aquaactress" themselves give the Deck consistency, as "Aquaactress Tetra" is able to search "Aquarium" cards, which would otherwise be hard to get.
All "Aquarium" Continuous Spell Cards also have this effect: "If this card is sent from the field to the Graveyard: You can target 1 Aqua-Type monster in your Graveyard; Special Summon it, also you cannot Special Summon monsters for the rest of this turn, except Aqua-Type monsters.". This extends their support even further, giving the Deck a wide range of Aqua-Type utility monsters. By using "Magical Hats", you can Summon up to 2 Aqua-Type monsters from your Graveyard, and since it was done in your opponent's turn, you are free to Special Summon non-Aqua-Type monsters during your turn.
"Koa'ki Meiru Ice" can destroy Special Summoned monsters on the field, helping the player get over monsters it normally wouldn't, such as a Ritual Monster Summoned by using "Djinn Releaser of Rituals", or "Number S39: Utopia the Lightning"; additionally, its Maintenance cost requires you to reveal a Continuous Spell Card in your hand, which can be accomplished with any "Aquarium". "Mobius the Frost Monarch" and "Mobius the Mega Monarch" can destroy Spell/Trap Cards when they're Tribute Summoned; this lets you destroy your opponent's cards, but it can also destroy your own cards, triggering the effects of "Aquarium" cards to Special Summon Aqua-Type monsters, even a "Mobius" that was previously destroyed. "Ice Hand" can only destroy your opponent's Spell/Trap Cards, but it can Summon "Fire Hand" from your Deck, allowing you to disrupt even more your opponent's field.
"Mermail Abyssteus" and "Mermail Abysslinde" make great targets as well. The latter is used to Special Summon "Mermail" monsters from your Deck, helping you maintain field presence. Also, "Mermails" have access to three of the best Aqua-Type Xyz Monsters: "Leviair the Sea Dragon", "Number 101: Silent Honor ARK" and "Mermail Abyssgaios", and all of these can be Xyz Summoned by monsters Summoned with "Aquarium" cards. "Mermail Abyssocea" can also be used, turning "Abyssteus" into a Level 3 and a Level 4 "Mermail" monsters (although there are no Level 4 Aqua-Type "Mermail" monsters).