Egad, I hate to do this, but Alex posted a great method for killing an amoeba early, so I guess I need to come clean with my "kill a hydra with 6 MIRV nuke frigates with starting engine tech" strategy. I've shown this to Zirkahn and Cybersaber, but I don't know if they shared it with anyone or if any of you had figured it out.
All you need is MIRV nukes. No auggies or fusion/ion drives needed. Just design your frigates with nothing but battle pods and 2 racks of 2-shot MIRV nuclear missiles (don't make them FST or ARM, that slows the ship down). You'll know it's the right design because the ship will have a combat speed of 15. This will give your ships initiative. But you still have to use the right tactics if you want to use just 6 ships:
ROUND 1: At the start, move each of your ships as far to the left as you can get, and then WAIT.
When the hydra moves, he will be unable to get close enough to your ships to fire, and since you haven't fired any of your missiles yet he can't shoot them down, either.
Now, after the hydra has moved, fire each ships' missiles at it to end the round.
ROUND 2: for each ship, FIRST fire missiles, they will be grouped with the ones from the previous round (exploiting a known game bug). Then, for at least 4 of your ships, MOVE toward the hydra. This is VERY important, because the hydra will take the opportunity to kill these ships. You need this to happen, because every ship the hydra kills is one more missile that it didn't, and 6 of these ships can only put a total of 24 missiles in the air.
ROUND 3: Keep some of your ships in range, again to soak up some of the hydra's fire. At the end of round 3, your entire missile cloud should impact the hydra and kill it.
If you use 7 frigates, you should be able to kill it without sacrificing any of your ships. That's probably a better idea in a game, but it's cool knowing you can do it with only 6 if you need.
VARIATION (that sometimes doesn't work...): I have done this with 5 frigates a few times, but you have to self destruct a ship next to the hydra usually, which is not always possible because they may all get shot down. I've failed with 5 more often than I've succeeded.
Note that this may not work if you are playing a -20 ship offense race. Have fun!
-Gusset