Algae is kikkin' my butt ?

[Bob I]

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I figured perhaps the evil nutrient must either be Iron or silicate. Only the 90g has lava rock so thats where I conjured up a suspision Iron may be leaching...

Why not think the other way, as in perhaps there are no "evil nutrients" at all. I am dreaming that perhaps you brought the stuff in on a rock, or something else, and it just likes it at your place.

If you go that route there would be no harm in removing the offending material, as there is really no cause, and removal would cure the problem.

I hope you can see where I am going with this.