I went there about a month and a half ago on my lunch break from Bethesda and what a waste of time.
The "boss" was there but after waiting for him to finish with another customer who, I actually had to ask him "Could you help me?" (I was the ONLY customer in the shop at that point in time) I asked about having some kalkwasser then had to say it was the calcium supplement and he pulled this faded color, dusty, Kent Marine kalk bottle from the shelf and it was super expensive.
Nothing in the store is arranged in an easy manner, their prices are on par with Congressional and Aquarium One, it stinks (and not from the fish but from the other animals and mold), and they are the most unfriendly people I've seen at the local LFS's. They should probably also think about removing the old lead-based paint from the stairway going down.
I'd not recommend this place to anyone.