Boss Challenge
Frankenfish
▲ Boss side

Water element
Skills: Fires a water orb that deals area damage. After taking enough hits it teleports to another lane, then takes extra damage for 5 seconds. The only boss that does not summon Zobos.
Boss Challenge
Frankenfish
▲ Boss side
Boss Challenge
Frankenfish
▲ Boss side
Boss Challenge
Frankenfish
▲ Boss side
Boss Challenge
Frankenfish
▲ Boss side
Boss Challenge
Frankenfish
▲ Boss side
Boss info: Clash of Critters Wiki
Frankenfish is widely seen as the hardest of the boss challenges, and low scores against it are normal.
Lineup 1 is a staggered checkerboard. Lane 1 has Wobbler in row 2 and Surgehoof in row 4. Lane 2 has Serrabloom in row 1, then Sonarbat, Hyphoria and Solaflora in rows 3 to 5. Lane 3 has Cheerspring in row 2, Galewether in row 3, Tideon in row 4 and Frostique in row 5. Lane 4 has Voltverine in row 1, Rockwu in row 3 and Waveflutter in row 4, and lane 5 has Zapup in row 2 with Zapantler in row 4. Without the third form of the Drilleroo line, a checkerboard like this is the shape to use.
The two row 1 guardians soften everything that reaches them. Serrabloom strikes over and over in a small area and makes enemies fragile, and Voltverine attacks from the shadows with a paralysing area strike, turning briefly invincible as it hits. Sonarbat marks a wide area as fragile, so Galewether's lightning clouds and Zapantler's piercing spear land harder.
At the top end, fourth-form Lightning units supply the attack speed that stops the boss from hitting lane 5, at very high levels. Even so, that evolution is not worth rushing just for this fight, and Voltverine and Tideon do not have to be third forms here.
As substitutes, Blitzmane or Boltskipper can stand in for Zapup, Electroar for Waveflutter, Zapuni for Surgehoof and Voltfawn for Zapantler. Another alternative keeps the board but uses first forms in many cells.
Lineups are numbered in the order shown above, left to right, top to bottom.