How a merge happens
Two fish merge when they are the same species, on the same depth layer, and touch. The new fish appears at the point halfway between them, on the same layer, with a burst of particles and that species' merge sound. Only the Cosmic Whale never merges.
You rarely push fish together yourself. The fish do it. Each one keeps watch for a twin, and once it spots one it claims it and swims straight to it, while the claimed fish slows to half speed so the suitor can close in. If the pair has not met within 7 seconds, the claim lapses and both go back to wandering until one of them spots a partner again.
What a fish can "spot" matters:
- It sees in a cone about 140 degrees wide in front of it. Range grows with the fish's size and its own vigilance: about 175 to 230 units for a Fry, more for bigger fish.
- It also senses anything very close on any side, within about one and a quarter times the two fishes' combined size.
- A fish that is fleeing a predator or chasing prey drops its merge plan. Fear and hunger come first.
So the practical rule is: two twins that are near each other will find each other, and two twins on opposite sides of a crowded tank may take a while, or get eaten first.
Dropping well
The release zone is the top fifth of the tank. Tap anywhere in it and the previewed fish enters at that spot, nose down. You can drop again after 0.35 seconds. Two things stop a drop: the cooldown, and a full tank, which shows the message "reef is full, let them merge".
A dropped fish does not sink where you aimed. It bolts: for roughly one to two seconds it darts and weaves toward deeper water in a random first direction, trailing gold bubbles, then settles into its normal swimming. Your aim chooses where the dash starts, not where it ends. Aiming above a cluster of the same species still helps, because the new fish starts its dash inside their vision range.
Tank capacity
The tank counter at the bottom counts every fish in the reef, large or small. It starts at 14 and rises by 2 with each Bigger Reef upgrade. When it is full:
- you cannot drop,
- eggs cannot be bought,
- and the free Fry that normally drift in every 2.6 to 4.4 seconds stop arriving.
Every merge frees one slot. A full tank is not a loss, but it stalls you until fish pair up on their own.
Pearls from merging
The merge that creates a species pays a base amount that rises quickly with the ladder: 6 pearls for a Neon Tetra, 20 for an Angelfish, 56 for a Koi Dragon and 110 for a Leviathan. The full list is in the species chain. Two multipliers can raise it.
Combos
Each merge opens a 2.5 second window. Another merge inside that window extends the combo and resets the window. The multiplier on the merge payout starts at 1 and grows by 0.25 with every merge in the chain, capping at 3:
| Merge in the chain | Multiplier | What you see |
|---|---|---|
| 1st | x1 | Normal merge |
| 2nd | x1.25 | COMBO x2 |
| 3rd | x1.5 | COMBO x3 |
| 4th | x1.75 | MEGA COMBO banner and confetti |
| 5th | x2 | MEGA COMBO |
| 7th | x2.5 | MEGA COMBO |
| 9th and later | x3 | MEGA COMBO |
A combo breaks when 2.5 seconds pass with no merge, and also instantly when the Spikefish kills or devolves one of your fish.
Combos reward cascades. Picture four Fry in a tight group: the first pair makes a Neon Tetra for 6 pearls, the second pair one more for 8 (6 x 1.25, rounded), and if those two Tetras meet within the window they make a Clownfish for 18 (12 x 1.5). That is 32 pearls instead of 24. The bigger the species at the end of the cascade, the more the multiplier is worth, because it multiplies the largest payout last.
Bloodlines
If the newborn fish carries one of the five rare bloodlines, its merge payout (after the combo) is tripled, and a separate bloodline prize is added on top. The prize can be worth far more than the merge itself. How bloodlines are inherited and what each one pays is in mutations and pearls.
Every other source of pearls
| Source | Pearls |
|---|---|
| Living fish (idle income) | 0.14 per second per step of the ladder: 0.14 for a Fry up to 1.54 for a Cosmic Whale; doubled for a bloodline fish |
| Pearl Rush boost | Doubles idle income for 2 minutes |
| Time away (over 2 minutes) | Half the idle rate of the fish you left, for up to 8 hours |
| Netting a Spikefish | 20 |
| A Manta Ray beating a Spikefish head on | 12 |
| One of your predators eating a smaller fish | Its rung number on the ladder (Angelfish 4, Leviathan 10) |
| First Cosmic Whale of the reef | 500 bonus |
Idle income adds up more than it looks. A full starting tank of 14 Neon Tetras earns about 3.9 pearls a second; the same 14 slots holding Pufferfish earn about 9.8. Upgrading your fish is upgrading your income, which is one more reason to merge rather than leave pairs sitting apart.
On the Welcome Back screen after time away, you can collect the amount shown, or choose the doubled option. If no video is available, the doubled option costs half of the offline amount in pearls, so it still nets you the other half extra.
What does not score
- Dropping fish pays nothing by itself.
- Fish lost to predators or the Spikefish are simply gone, along with their idle income.
- The species counter in the HUD (found this reef, out of 11) is a progress marker, not a score.
The pearl total is the only number the game keeps for a reef, and your lifetime total counts toward the 25,000-pearl achievement.