amonia level out of control

Question
I will begin by giving a quick history of my tank.  It is a 29 gallon fresh water tank approx 3 and 1/2 years old.  First month spent cycling with danios, next 6 months adding fish.  With the exception of a few fish deaths due to angels fish incompatabilies (lost some fancy guppies and neons to the angels), tank has been happy and healthy.  I faithfully do monthly filter changes and maintenance along with partial water change and vacuum silk plants and gravel. Until about 2 weeks ago, had danios, skirted tetras, cory cat, silver hatches and a small pleco.  Found the pleco (over 2 yrs old) dead.  Ammonia level was elevated.  Did a partial water change with no relief.  Have been doing 9-10 gallon water change every night for the past 2 weeks with only minor drop in ammonia level.  Have now lost a few hatches.  The only thing different that I have done is about 3 weeks ago, I got a battery operated gravel cleaner/ sludge extractor.  Worked nicely, but maybe this stirred up the gravel too much.  Don't know what else to do beside water changes.  Please help if you are able. Thanks so much!

Answer
Hi Debbie,
  The problem is that when a pleco dies, it really pollutes the water.  I have had one dead pleco kill an entire tank in one shot.  I suspect it has to do with a particular chemical (called shrekstoff) which plecostomus and other catfish have in their bodies.  

  In any case, water changes is the way to go.  I am glad that you are doing them more frequently now.  Once a month is not really enough.  Ideally you should be changing 25% of the water once a week, every week.  If a fish like a pleco dies, do them more often -- even once a day for a few days - until the tank stabilizes a bit.  

-- Ron C.
  rcoleman@cichlidresearch.com
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