How long is the tank? If its the same length as a t-5 bulb, I would definitely go with a t-5 set up. If you want the shimmer, do a t-5 and MH set up.
As for the 400Watters, it depends on what you wish to keep on the bottom. Also, I would look at sanjays website to compare 250DE to 400SE bulb and ballast wise. This way you can get the best possible output for the least amount of money possible. And remember, when you add in the better reflectors available for the DE bulbs, the output is often comparable for those two types of set ups.
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