Overdo it? Hah! I laugh in the face of overdoing live rock!
If you're talking about what is marketed as Maiden's Hair in my area, (seeing as we all know names are abused in the pet trade) Maidens Hair does NOT do good in a high nitrate environment. Maidens Hair is a calcareous algae, fish won't graze it, it doesn't grow very fast, and it's pretty worthless for exportation of anything other than calcium. Same with shaving brush, mermaids fan/maidens fan, and that dollar shaped looking stuff (can't remember the name but it looks like a chain of coins). Caulerpa is fantastic at lowering trates and phosphates but it is dismal for water quality, because it constantly sheds noxious compounds and "greening" agents. If you use caulerpa, activated carbon is a MUST. And frequent trimming. Chaeto is good because it is generally, if properly illuminated, grows like a weed. And it makes a great home for pods
. Gracilaria is good too, slower growing, but infinitely edible to most tangs and blennies.
It should also be pointed out, that if you're using a commercial hob
fuge, more than likely it won't be big enough to do any real amount of nutrient export. The true purpose of a refugium is to give a safe place for pods
to grow and breed. If you want to do nutrient export, you'll require a much larger refugium, preferably bare bottomed or with a 3 + inch deep sand bed of fine oolitic sand, and a powerful 6500 spectrum light. The other option would be a algal turf scrubber.