A technique in the works.

This is my first time making a technique, and considering that I haven't relly played the game (only read the 5th ed. book repeatedly), I need a little help making spells.

I had an idea for a spell called Neptune's grasp, where by the magus is able to control two columns of water, and twist them and shape them at will. they act more as an extension of the casters arms.
The columns reach, and size are determined by the body of water the columns are shaped from. and if the water is severed from the original column, or the column cut from the original source of water, the water falls to the ground.

As per the rules, it has a base of 10 with +3 magnitudes for changing range to sight. +1 for changing Duration to Concentration, and +1 for changing target to Part.

Neptune's Grasp, by my calculations, is a Magnitude 7, level 35, Rego-Aquam spell.

Is there any other modifiers I need to add to make this spell work? or is it good as it is? I used to more rigid rules for casting spells, so it seems as if I over powered it...

I just think you need to limit the size of the tentacles, or add magnitudes on size if you want it to be possible for them to be huge, even if depending on the body of water.

Not sure what you mean by "making a technique" - not sure at all, the more I try, so I'll just pretend you didn't say that.

To use the shorthand in the rules,

ReAq 35
(Base 10, +3 sight, +1 Conc, +1 Part)

That would get you an "extremely violent" effect, BUT not one that is in any way "unnatural" (see 2nd paragraph of Guidelines text.) And two "arms" of water rising up out of a pool is quite unnatural. Unfortunately, to use the two pillars like "arms/hands", you'd need to add +2 more magnitudes, to "very unnatural". (The advantage of this effect, with the addition of Target: Part, over "Waves of Drowning and Smashing" would, I'd think, be some additional precision in what the wave slams and what not.)

However, if you only wanted to manipulate things, and not punch them hard, you could back the Base down to as low as Base 1, which would give a "Gentle Hands" spell. Not combat oriented, but only Level 20. Or somewhere in between, depending on the final effect desired.

Also, some StoryGuides might draw a distinction between unnatural arms as punching/lifting, and unnatural arms as fine manipulators, and ask for yet another magnitude for "Complexity", a general catch-all. If so, might be better to create 2 spells, one for slamming ships, and another for saving drowning kittens, or whatever.

Lastly, the size of the arms is not based on the size of the pool (altho' it would be limited by that), but on the "Target" of the spell. If you wanted to control more than a base Individual amount of water, additional magnitudes should be added. +1 should give some pretty large "arms".

But, aside from that, yeah, you've got it. Welcome to Ars!

On the last Bit, I did mean to say limited in size by the size of the body of water. but lack of sleep makes for bad logic.