I definately wouldn't support a decrease in skill cost, a field full could kill alot with that xD
Did you realize that Piranhas can only attack 1 creature per turn? I dont think it would really matter.
Two opinions of mine: cost is too low, make it at least 2 
And about the ability, i think it's too powerful if you make it mono-element.
I think you can make it free if the piranhas are underwater (buff for flood) or make it of another element. Maybe 
or 
, i don't know what will fit best.
Well, we are going to change the skill like that, the cost increase wouldnt be necessary, would it? 2 quanta for 1/2 creature? But about changing the cost itself, I think it would eventually kill the card, not worthy even with Fractal or Mitosis, like Scarab. And water already has some sinergy with death, that Im not wanting to strenght this time.
Im still not convinced at all that a nerf is needed. Considering how low its the attack and how specialized should be a deck to use them with Fractal or Mitosis, Im not really worried about it being OP. Although, Im really thinking about increase cost and decrease skill cost.
Mhhh... thinking again, they can only kill small creatures, like 2 or 3 HP. To kill something bigger, you need more turns, or 6 Piranhas in the field (if an opponent let you play 6 piranhas, he definitely deserves some punishment!) or some combo (fractal, mitosis), or some buff for the creatures.
So i guess you can lower the ability and raise the cost.
Maybe add a delay when they bite unless they're underwater? It's not too critical, but i think it's fitting.
