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. Players can only have one Aquarium at a time, but it can be removed and placed somewhere else without losing any progress. The Aquarium is one of the few updates for 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
Before purchasing prawn perks, every 35,000 life points worth of aquarium-related fish fished by the player will receive either a prawn ball, prawn cracker or golden 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, 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. Right clicking the bathysphere gives you the option to view your fish list showing you which fish you have found and which ones you still need. 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 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.

If the aquarium is removed, any fish unlocked remain after the room is rebuilt, but all furniture will be lost.

Strategy
Because you receive prawn balls based on how many life points the fish heal, 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. If you are 99 Fishing, you can get 50 free Prawn balls by talking to the Prawnbroker, which should be done first as it may provide your first Golden eggs and Prawn pennies/pounds. As eggs are caught, they should be added to the aquarium and the rewarded Perks cashed in. The recommended order of Perks is:
 * 'Greater chance of receiving Prawn Balls'
 * 'Gain a landmark of your choice' - Fremennik longboat decoration
 * Rest of Tier 1 perks
 * Tier 2 perks
 * 'Prawn Pennies and Prawn Pounds last 2x as long'
 * 'Greater chance of receiving Prawn Balls'
 * Rest of Tier 3 perks
 * Tier 4 perks
 * 'Greater chance of receiving Prawn Balls'
 * Rest of the perks

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.

Right click options on bathysphere are:
 * Operate - takes you into aquarium in your dive suit
 * Clear floor - removes all items from the aquarium floor. Requires building mode. Items unlocked will still be unlocked.
 * View fish list - shows a list of all fish found and counts of Prawnballs found (up to 200+). Allows you to track Prawn perk progress

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 through Gameplay Settings.

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.

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%. The decorations do not have to be placed inside the aquarium in order to get the bonus experience; they only need to be stored in the bathysphere.

Prawn perks
Prawn perks from a certain tier can only be activated if all of the perks from the previous tiers have been activated.

Tier 1

 * Greater chance of receiving Prawn Balls
 * No-Bait fishing (doesn't work with Rocktail fishing or Barbarian 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

 * Golden mystery egg

Tier 3

 * 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

 * Golden Prawn Cracker (Golden fish egg if ironman)

Tier 5

 * Greater chance of receiving Prawn Balls
 * Barbarian fishing without needing any bait (i.e. feathers, fishing bait, fish offcuts, roe or caviar)
 * Great White Shark Pet and Great White Shark in your aquarium
 * Ability to fish Great white sharks from shark fishing spots

Tier 6

 * 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 and underwater decorations 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. While in building mode, open the interface that lets you place items in your tank, then remove your first plug, and select from the menu the next plug. As before, go into building mode and remove, then select from the menu the next one. The second prestige will give the player a Stone of Jas plug.

As of 27 April 2015, prestiging can unlock new barehand fishing animations that can be toggled from the Prawnbroker. The first prestige unlocks silver fishing and the second unlocks gilded fishing. Although it is a skilling animation, the animation cannot be toggled from the Animations interface.

Trivia

 * On 27 April 2015, an update was added that allowed for Aquarium decorations to stack in your inventory. Players who already had several of the same item already in their inventory had each item stacked individually.
 * In the same update, bare-handed fishing animations were graphically updated, to reflect the fish seen in Aquariums.
 * Aquariums were a largely player driven update. Mod Osborne gave credit to a number of players who helped the development process.
 * Trout, salmon, and eel are anadromous fish species; born in fresh water, spend most of their life in at sea, and return to fresh water to spawn. It was originally questioned how "The Aquarium can somehow sustain both freshwater and saltwater fish at the same time."
 * The examine on the Bathysphere "A rapturous construction." may be a reference to the video game series .