- As a rare reward from fishing tuna (level 35 Fishing required) -- approximately 3 hours on average to get the egg.
- From the golden mystery egg, which gives you a random fish egg you do not already have, with no Fishing requirement. Golden mystery eggs can be obtained from prawn balls (1/200 chance), or as a 100% reward from using a golden prawn cracker (or having it used on you). One golden mystery egg is also the tier 2 prawn perks reward from the Prawnbroker.
The eggs can be used on the bathysphere in your aquarium to put a tuna inside the fish tank. Putting it in the tank will unlock one prawn perk, which can be spent at the Prawnbroker.