Both Clown Fish dead 2 weeks apart!!

I mixed it with water then poured it in the area with the bio balls? What is DT?

 

display tank

 

I have had this to happen once and I have known many to also have the fish to all die off at around 9 weeks , This is why I allow the system 12 weeks after 10 weeks its not that common But between 8 and 10 weeks there can sometimes be a sudden ammonia spike and it will shoot off the charts and be gone in hrs . I set up a reef for a customer in Va at a Beauty shop they just had to rush it and about the middle part of the 10th week he called to say all my fish are gasping at the surface and he had tested the water and Ammonia was very high . Seems a LFS sold him a few fish and they put them in about the 5 and 7th week lost them all .. LES guru said oh heck yes its cycled ..

Here is another thread with about the same deal

http://www.3reef.com/forums/new-hobby/brooklynella-nitrite-ammonia-poisoning-64398-2.html

 

Thanks for the advice. Questions - If the tank did have an ammonia spike wouldnt my inverts and coral been affected also?