I can't really see this being all that useful. I mean it's a lot of damage to pack in one card, but you need four heads and five turns before the damage : quanta ratio breaks even. 4 x 5 + 1 | 4 x 3 + 9 = 21 | 21. Plus its susceptible to all sorts of control- especially with heads being only 1 HP. Maybe with the new shard + Flooding coming this might be good, but that's not finalized yet- but even that would be a really specialized deck with still a tonne of weaknesses and straight up hard counters.
FFQ, Pharaoh, and Steam Machine are all similar to this card and all sound great on paper but in reality aren't all that useful, being both slow and susceptible to control. For example Steam Machine (because they are both straight damage): 4 Water, 4 Fire, and 3 turns gets you 8 damage, gaining 4 damage every turn for two fire quanta- which is better than this card (as it is faster) but still not that great.
A possible change:
6
Hydra: 0|11
Spawn Hydra Head
Hydra Head 5|2
10 Quanta and 3 turns gets you 10 damage. Though actually you might want to change the ability cost to Life. I know Water has enough off element abilities and could use more mono power but you're gonna probably want to use some EBonds anyways to compensate for the fact that this is slow to setup, and a life ability cost would help balance the quanta usage.