high nitrate, High alkalinity

Question
QUESTION: Hi Michael,
I just set up 45g tank for 5 weeks, I use canister filter (jebo) and Prizm pro deluxe skimmer.  At first, my nitrate level was not that bad (5), and now it is boost up to 55. I changed about 25 gl water within a week, and cleaned/changed the carbon in canister filter as well.  But my nitrate is still high (just down a little).  I have lost 2 firefish, 1 gubbie, 1 sailfin tang, 1 powder tang within 1 week, however all my anemonea, sun coral, brain are doing well.  I do have a sea apple in my tank.
1) how to lower nitrate level, somebody suggests that I should remove all pads & ceramic medias in canister filter and use only carbon media instead.  Is it ok?
2) Is sea apple a problem for my death fishes?
Thanks
Hanson


ANSWER: The sea apple does emit a poison if stressed, But unlikely. Now here is my guess, i usually take longer than you did to cycle a tank, and add fish slower. removing the pads and ceramics will help a little. Other than that keep up on the water changes once a week. Let it cycle for another 2 weeks without adding any livestock, and when you are ready to add your fish again 1 or 2 at the most, at a time.

---------- FOLLOW-UP ----------

QUESTION: Can I put Nitrate Sponge in my canister filter for lowering Nitrate? Any chemical like de-nitrifying is available to use?
Is it OK to use canister filter for 45 gl (fish & coral & live rock, sand)? Thanks

Answer
Try to stay away from chemicals, yes it is ok to use a canister filter. Ok now I know more about your tank, if it is only five weeks old, your problem is it didn't cycle fully. Do not put anymore livestock in your tank, you are most probably having die off from your rock and sand. Keep up your water changes, and keep testing, I would let it go for another 2 weeks maybe more. Leave your sand and coral and let the process complete. My friend patience is the key, to getting it right the first time. Look up some info on a refugium, I would consider adding one. I use them with great success. They are easy to build also with spending an arm and a leg. Oh, watch your sea apple if it die's remove it from your tank right away. Let me know if you need more info. I have been in the hobby for over 12 years, and from past experiences, it now takes me aprox. 6 months to set up a marine aquarium.