Can a frag tank be too shallow?
 

I found a good price on some large footprint holding vats but they are only 7" tall. In your opinion Is 6" of water too shallow for a grow out system and why?

Grow out yes too shallow. But perfect for frag tanks

IMO.. I would think lighting is going to be tough... almost anything over a tank that shallow is going to be intense, and with only 6" your won't really have room to acclimate to the lighting, at least in a "start at the bottom and move to the top" sense.. and as things grow or you add new, adjusting your light height may end up frying the tops of "older" frags or not having enough light at the bottom for "newer" ones...
Powerheads aren't "small" either.. figuring out your flow pattern might be tough given the lack of space to mount them...if you need them that is...
Not saying it couldn't work... just some things to think about...

Our LFS has a 6" deep frag tank. He runs T5/T8's over it if I remember right about 4' above the tank. Everything is growing nicely in there.

My thought was to use a light mover to reduce intensity. The tank is 4ftx8ft so maybe a 3ft t5 fixture hung high on the mover for less light out wide. I would think a closed loop system would be great to keep waste suspended.

IMO Im not a fan of the 7inc frag tanks, its a bit too low for me. As stated, doesnt allow much room for grow out, Also in my eyes the biggest problem is if its a mixed frag tank theres no way to regulate flow or par for each coral needs because a tier system is not an option. But, if your intent is to make this a dedicated sps/lps/softie frag tank i think it would work fine.

I would ideally make 2 separate systems. One for sps another for lpc and soft corals. These would be more for frags to heal over and encrust. Two of these vats would be aprox $600 which sounds like a good price for the footprint I would get

How big is the footprint?

4ftx8ft

Would a 7ftx2.5ftx1ft tall be better for what I'm looking to do?

From whom are you buying these? Local or mail order?

interested as well. Can you post a link to your source?

They are hydroponics trays and reservoirs. Made of abs which from my research seems to be reefsafe. They are also built to hold water. I was looking into the Bonticare brand 4'x8 tray and the 100g ezdrain. The 100g was not flat bottomed but was deeper with smaller footprint. You will need to search to find the place with the best shipping to you. Here is a link to where I was looking. Shipping was better with 8' because it wasn't thru ups.
http://eastwesthydro.com/category/hy...raysreservoirs