Aquarium

The Aquarium is a room in a player-owned house where players can showcase their Fishing skill. Building an Aquarium requires level 63 Construction and 200,000 coins. The room was suggested on the forums and chosen by players in a Player Power poll. The Aquarium can only be built on the ground level, and has 4 doors. The Aquarium is one of the few updates of which a design document was made public.

There are five types of hotspots available and special objects for underwater usage:
 * Centrepiece wall - Scenery.
 * Diving suit - An outfit that allows certain daily and weekly rewards to be collected.
 * Supply - Scenery.
 * Prawnbroker - Location and type of shack the Prawnbroker resides in.
 * Fish-head - Scenery similar to the big fish in the Skill Hall.
 * Underwater - Scenery and rewards accessible through certain diving suits.

Fish
Every 25,000 life points worth of fish fished, the player will receive either a prawn ball or prawn cracker. The prawn balls can be opened by one player, while the crackers have to be used on another player, and both will get a reward. Once in a while when fishing (on average, about every 3 hours), you will receive a golden fish egg of the type you are fishing, so long as you don't already have that egg. You can also get golden fish eggs from prawn balls or crackers, from golden prawn crackers, from the Motherlode Maw, or once from the Prawnbroker. Players may toggle the option to receive prawn balls while fishing by talking to the Prawnbroker.

There are fourteen golden fish eggs to collect, and you can put the eggs in the bathysphere to make a fish appear in your aquarium. Each egg collected will let you unlock one of the fifteen prawn perks at the Prawnbroker. You can also get four more prawn perks by collecting 1, 20, 100 and 200 prawn balls. Unlocking all 15 prawn perks is a requirement for the completionist cape, and collecting all 18 prawn perks is a requirement for the trimmed completionist cape.

An additional aquatic creature, the great white shark, is unlocked at the same time Sayln the Shark is purchased from the prawnbroker. Unlike the other creatures, the Great white shark is not lost when the plug is pulled.

Optimal order for the most Prawn balls
Because you receive prawn balls for every 25,000 life points worth of fish, you should generally catch fish that give the highest life points per hour, until you've received that egg, and then potentially move on to the next best. This table lists the 14 fish approximately in order of life points fished per hour at 99 Fishing.

Decorations
Some decorations are included with the Aquarium by default and some must be obtained from prawn balls and from fishing. Before you can use new decorations you must add them to your Bathysphere by clicking on them and then clicking on the Bathysphere.

Bathysphere
The bathysphere is an uncustomisable part of the surface level of the Aquarium. It allows the player to traverse down into the underwater portion of the Aquarium. When activated through building mode, the bathysphere allows access to the customisation interface for the underwater portion of the aquarium. The maximum number of objects that can be placed inside the aquarium is 30.

Diving suit
You need a suit to enter your aquarium. Better suits let players open better decorations. The oyster hunter suit lets players open oysters, the mermaid hunter suit lets players additionally open Mermaid's purse decorations, and the Salvage hunter suit lets players additionally open Treasure chest decorations.

Prawnbroker
The prawnbroker lets players unlock prawn perks, which improve Fishing in a variety of ways. You can also toggle the passive prawn perks effects and prawn ball drops with the prawnbroker, or cash in unused perks for 10,000 Fishing experience.

Underwater
The underwater portion of the Aquarium is uniquely different from the rest of Construction. It has its own hotspot creation tool where items are obtained from prawn balls and prawn crackers or obtained by default. Items removed using the right-click option on the aquarium construction screen are not destroyed but sent back into your pool of buildable items.

Cosmetic

 * Anchor (from prawn ball)
 * Cannon (from prawn ball)
 * Coral reef
 * Cracked pots
 * Boot
 * Rocks
 * Ship bow
 * Ship stern
 * Cannon
 * Anchor
 * Castle
 * Stone head

Rewardable

 * Seaweed and Kelp (Aquarium) can be retrieved every 24 hours for minimal Farming experience and two of each item.
 * Oysters can be opened every 24 hours if a player has built the Oyster hunter suit or better. It has access to oyster pearls and the Prifddinas gem-rock table.
 * Mermaid's purse decorations can be opened every week for 20 mahogany or teak planks if the player has built the mermaid hunter suit or better.
 * Treasure chests can be opened every week for one clue scroll (elite) if the player has built the salvage hunter suit and does not already have a clue scroll.

Experience
Experience decorations increase the chance of finding golden fish eggs at certain fishing spots. They also increase the experience given at those fishing spots by 2%.

Tier 1 Perks

 * Greater chance of receiving Prawn Balls
 * No-Bait fishing (doesn't work with Rocktail fishing)
 * 10 Prawn Pennies
 * Gain a landmark of your choice (if you already have all landmarks you will receive 10 Prawn Balls when selecting this perk)

Tier 2 Perks

 * Golden mystery egg

Tier 3 Perks

 * Greater chance of receiving Prawn Balls
 * Fly fishing without feathers
 * Prawn Pennies and Prawn Pounds last 2x as long (50 and 200 charges respectively)
 * Gain 3 diving suit cosmetic overrides for the surface

Tier 4 Perks

 * Golden Prawn Cracker

Tier 5 Perks

 * Greater chance of receiving Prawn Balls
 * Barbarian fishing without bait or feathers
 * Great White Shark Pet and Great White Shark in your aquarium
 * Ability to fish Great white sharks from shark fishing spots

Tier 6 Perks

 * Ability to make sushi

Prestige
Once the Aquarium has been filled with all fourteen fish, the Standard plug decoration can be used. It will reset the Aquarium's caught fish but the Prawn Perks will not be reset. There are warning messages to ensure that the player understands what will happen by using the plug to prestige.

The first prestige will give the player a Chinchompa plug. The second prestige will give the player a Stone of Jas plug.