Suggestions by @laylachat

Koi (Fish Hooks)

as Koi in Aquarium

Coral the Betta

as Betta in Aquarium

Enguarde the Swordfish

as Marlin, Swordfish in Aquarium

Kala Mer'ri

as Squid in Aquarium

Grandmama (Ruby Gillman: Teenage Kraken)

as Squid in Aquarium

Squidly (591)

as Squid in Aquarium

Squid Undead

as Squid in Aquarium

Mackraken

as Squid in Aquarium

Mutant Giant Squid

as Squid in Aquarium

Giant Squid (Finding Nemo)

as Squid in Aquarium

Giant Squid (Harry Potter)

as Squid in Aquarium

Colossal (FNaF)

as Squid in Aquarium

Abyss the Squid

as Squid in Aquarium

Kraken (Skull Island)

as Squid in Aquarium

Tech Kraken

as Squid in Aquarium

MarineDevimon

as Squid in Aquarium

Electric squid

as Squid in Aquarium

Yin (501)

as Squid in Aquarium

Gesomon X

as Squid in Aquarium

Gesomon

as Squid in Aquarium