nitrite levels are crazy!

Question
QUESTION: hi my names eajaz and having read your responses to peoples questions i was wondering if you could me?
i have a 30 gallon fish only marine tank, i have about 7 fishes in their, 3 very small blue damsels, 1 tiny clown fish, 1 coral beauty,1 yellow tang, and one spotted back tang, the yellow tang is stressed and has not eaten in about 3 days now, my nirite levels are over the chart, 1 other tan i had died becuase of this today, i had done 4 water changges each at 25percent, i have added salt, i had put some rocks in thier which the fishshop said would help, and i have added about 40ml of bacterlife, but still their is no change and i fear the yellow tan will die soon, i have one internal filter, but i added all the fish within about 3 weeks of the tank setup, i am waiting for an external filter to arrive very soon which i will keep on along with the internal filter. what do you think? what shall i do?
ANSWER: Hello eajaz,
A couple of things.
First, keep up large water changes. I suspect the fish have died from nitrite and ammonia poisoning. Water changes will help that.
Have you also checked your ammonia levels?
Have you checked nitrite and ammonia in your tap water just to be safe?
Bacterlife is a product that is unproven.
You need to get Bio Spira and your tank will cycle maybe over night.
In the meantime, when your new filter arrives, I am sure that will help too.

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

QUESTION: thankyou very much for the quick response, the information you have provided has been very helpful, i will carry on with the water changes and i will let you know when the external filter arrives, i have a feeling i will have some problems with the new filter too, but thankyou very much for your response, much appreciated.

i was wondering what i should do when the new filter arrives? should i just set it up and run it on the new pads that come with it and keep my internal filter in too? or shall i use the old pads from the internal filter? and would you happen to know many fish i could keep in my tank? and what should i do about the yellow tang which at the moment is just hiding away and will not eat?

thankyou for your help and i shall try and get hold of bio spira.  

Answer
Hello eajaz,
When the new filter arrives just run it with the new pads, but don't take the old filter out for at leas 3 weeks until the new filter developes it's own "good" bacteria. Even then, 2 filters are better than one.
Generally, the "rule" is one inch of fish for every 10 gallons of water but there are exceptions.
You wouldn't want to put a 30 inch fish in your tank, so your choice of fish is important.
If a fish is expected to grow 3 inches at maturity, then you can have 10. If you use smaller fish, then you can have more.

As far as the yellow tang, I don't know. Just keep changing the water out until you can get the Bio Spira and hope for the best. He sounds very stressed and sometimes they don't pull through.
In case I didn't mention it, when you add the Bio Spira, don't do any more water changes until the ammonia and nitrite levels are normal
Good luck!