WoWDB

This achievement became a Feat of Strength in 4.0, but it is still achievable - with the same restrictions of having done it at "current content" level.

The requirements for players:

        • Must be level 80.
        • Armor must be ilvl 226 or lower.
        • Main Hand/Off-Hand must be ilvl 232 or lower.

        (basically no ilvl higher than what you can earn in Ulduar 10man)

Functionally, this means getting a toon to 80, turning off XP, then farming either Ulduar 10 HMs, Ulduar 25 normals, TOC5 heroic, and/or ICC 5 normals until you have a good gear set.  Heirloom gear has an item level of 1 and is allowed.  Many slots can be purchased using Justice Points, or made with Ulduar-drop crafting patterns.  Justice Points can be farmed by running Cataclysm 80-85 normals (this may require you to do some early Vashjir or Hyjal quests to build a gearset with high enough item level).  Wrath level gems are typically cheap and easy to get, and can also be bought with Justice Points.  You can also use Profession bonuses and Cataclysm level consumables, which will be a significant boost.  Personally I recommend everyone in the raid have an average of ilvl 219+, better for tanks and healers who have the hardest job.

Everyone in the raid MUST meet the requirements at all times.  One person messing up will void the achievement for everyone.  

The DPS requirements on Algalon are easy to meet and he still hits like a truck on tank, so I recommend running 2 tanks, 3 healers, and 5 DPS and following normal Algalon boss guide strategy.

As of the latest item level squish, this achievement now requires item level 100 or lower.  Make sure you are not using heirloom gear in any slot.  At character level 80, heirloom item level is 103.  Godspeed.