[StirCrazy]

I see a couple issues here, and need a bit more info. do you only have MH right now? no other lights? if so, depending on what color you are running for your MH adding T5's to fill the gaps is going to look horable unless you can match the T5 color to your MH color. I will explain farther.

for your 4 (front to back) T5 way, if you can't match the color you are going to end up with definded strips of light, we will pretend your using bluish lights and call the T5s B1 and the MH B2, so you will start at one end and have [b1] [b2] [b1 - b1] [b2] [b1] and due to the orentation it will be quite noticable.

lenthwise will be better as you will be lighting the whole tank with the T5 color then you will just have the spot light effect of the MH punching through the T5's so it might end up looking like you have two sun sources punching through the blue water.. does that make sence to you?

the best option would be to add two 4 foot T5s one front one back AND add another MH. 5 foot is a tough lengh, I lit a 3x2x2 tank with two SE HQIs, and would probably use 3 on a 5 foot tank.

now another option would be to add the two 4" T5's but raise your pendants up to spred the light a little more.. 6 to 8" should do it but you would have to play with it to fid the spot that gives you a look you like. Heck befor you go spend money on T5's try raising your pendants a bit to see if you can spread the light.. if so then your done.

cost wise, two T5's are cheeper than 4. problem is doing it this way you arn't going to have a fancy fixture so the T5's will basicly only be there to even out the light a bit.

Steve