Vacation Mishap

Question
We went on vacation for 4 days and came back to a tank full of dead fish.  We have a 90 gallon saltwater tank, it's been up and running beautifully for about a year.  We are suspecting overfeeding by our petsitter but we want to get our tank back into shape to start restocking.  The only thing we have left are two engineer gobies and a chocolate chip star fish along with the live rock, which amounts to about 150 lbs.  We did a partial water change last night (25%) when we arrived, took out all of the dead fish and I added some Ammo Lock.  I tested the ammonia this mornign and it is still off the charts, nitrates are high as well.  What is the best thing to do to get everything back quickly and safely so we don't lose the gobies as well?  I am headed to the pet store today to get new filter media.  My guess is that the fish started dying Friday and we found them on Sunday.  Help!

Answer
Hello Chrissy. The best thing that you can do is a very large partial water change(about 50%). Changing the filter media will help also. It may take several large partials in order to get your tank back to how it was. From my experience adding chemicals like ammo lock is not always a good choice. Some of these chemicals will actually neutralize the harmful effects of ammonia but not remove it from the tank. Your testing may still show that there is ammonia in your tank. You may not get a very accurate reading. Doing partials is the best(and in my opinion the only way) to properly rid a saltwater tank of nitrates and ammonia. You can do a 50% water change once a week or several smaller ones every other day. Contrary to popular belief large partial water changes done frequently will not harm your good bacteria and any time your water quality goes south removing some of that water and adding clean water is a good choice. Be patient and diligent about testing and eventually it will come around.