The Spikefish
The Spikefish is the only enemy in Leviathan. It is a small red fish covered in spines that swims in from outside the tank, picks the nearest fish it can hurt and charges it. It is small and fast, it ignores the two depth layers, so no fish is safe by being in front or behind, and it does not stop to eat: whatever it touches is resolved instantly.
When it comes
The reef checks for a Spikefish on a timer. The first check comes 55 to 70 seconds after you start or continue a session. A Spikefish only appears if all of these are true at that moment:
- the tank holds more than 10 fish,
- at least a minute has passed in this session,
- fewer than two Spikefish are already alive.
After each check, the next one comes 31 to 41 seconds later during the first three minutes of a session, and 21 to 31 seconds later after that. So a busy reef sees a Spikefish roughly every half minute, and two can be in the tank at once.
The very first one in a reef is introduced by a card that pauses the game and explains what it does. When you close the card, the Spikefish swims in right away, with a pulsing "TAP TO NET!" marker above it.
The warning
Every later Spikefish is announced 1.4 seconds before it arrives. A dark shadow with red eyes looms at the left or right edge of the tank, at the exact height where it will enter, and a warning sound plays. Then the Spikefish swims in from that spot and the music switches to the threat theme until the last one is gone.
While it is still swimming in from the edge, it travels in a steady, nearly straight line and does not chase anything. That entry glide is the easiest moment to tap it.
What it does to each species
Once inside, it targets the nearest fish within 340 units that it can affect, aims where that fish is heading rather than where it is, and speeds up when locked on.
| Victim | Result of contact |
|---|---|
| Fry to Koi Dragon | Killed outright. The Spikefish survives and keeps hunting. |
| Anglerfish | Knocked down to a Koi Dragon. The Spikefish dies in the exchange. |
| Manta Ray, hit head on | The Manta wins: the Spikefish dies, the Manta is unharmed and you get 12 pearls. |
| Manta Ray, hit from the side or behind | Knocked down to an Anglerfish. The Spikefish dies. |
| Leviathan, Cosmic Whale | Nothing. It does not even target them. |
"Head on" means the Spikefish is within roughly 70 degrees either side of the direction the Manta is swimming. Every kill or knock-down also breaks your current combo.
A knocked-down fish comes back with brand new genes, so a bloodline Anglerfish or Manta Ray that gets hit loses its bloodline as well as a rung.
If nobody nets it, a Spikefish leaves on its own 16 seconds after it appeared, which is plenty of time for several kills among small fish.
Netting it
Tap or click on the Spikefish anywhere in the tank to hit it. The hit area is a little larger than its body, so a near miss of a few units still counts.
| When | Taps to net |
|---|---|
| First 250 fish you drop in a reef | 1 |
| After that | 2 or 3, equally likely, decided when it spawns |
A hit that does not finish it flashes it white, freezes it in place for 0.3 seconds, nudges it upward and shows "hit! N left". The freeze is your window: tap again just above where you hit it. The final tap nets it for 20 pearls.
The drop count that decides this starts again from zero in each new reef, so the start of every reef is the gentle one-tap version.
How your fish react
Every species up to the Anglerfish shies away from a Spikefish within 180 units and swims about half again as fast while one is within 160. In open water that is enough for most small and mid-sized fish to stay ahead of it. The slow swimmers are the ones that get caught: a Pufferfish or an Anglerfish is usually slower than a Spikefish even at full speed, and any fish pinned in a corner or boxed in by a crowd has nowhere to go. Fish also keep fleeing their usual predators at the same time, so a crowded tank under attack scatters in every direction and breaks up pairs that were about to merge.
The threat inside the tank
Your own fish are the other hazard. Any fish eats fish at least three species smaller than itself, and from the Angelfish up they hunt actively. The three giants, the Manta Ray, Leviathan and Cosmic Whale, only eat the first six species. The species chain lists exactly who eats whom. Two things make this more than a footnote:
- It drains the bottom of your ladder. A Lionfish eating a Clownfish removes four Fry worth of work and pays you 6 pearls for it.
- It never stops. Unlike the Spikefish, a predator is always in the tank. The Anglerfish is the quickest eater, ready again 1.5 seconds after a meal.
The full tank
The last kind of pressure is space. A full tank blocks drops and eggs, and stops the free Fry. Space is also tied to the Spikefish: it only appears when the tank holds more than 10 fish, so a reef that is crowded is a reef that is being attacked. Keeping merges flowing keeps both problems smaller. Ways to do that are in strategy.