sucker fish/algae eater

Question
we recently purchased two split tail goldfish,a dark algae eater, a tank(maybe 5 gallons), fake bonzai tree, and of course rocks.  We had no filter or air bubbles.  We did weekly water changes.  One day I accidentally left the gold fish food down low where my 2 year old could reach it.  She poured way too much food in.  My husband didn t notice until the fish had completely stopped eating, which takes a lot when there s still a lot of food in the tank.  He changed the water.  A few days maybe even a week later, one of my goldfish started swimming funny, and mostly acting like she couldn t swim down to the bottom.  I looked on the internet at things that could be wrong, of course the most obvious was swimmbladder. So we fasted her a day, which we had done anyway right after the incident occurred.  Had her in a small betta bowl (not with a betta of course), and she seemed to be doing well.  We put her back in the next day(adjusting water temp) and she was good for a few hours, and then back to what she was doing before.  We repeated the fasting 1 to 2 more times and then realized the other goldfish was starting to swim funny too. So I seperated all three of them, went to town, got a 2 gallon tank(granted it s smaller) with the air bubbles, a light for temp regulation(which I only turned on an hour at a time 3 times a day)bigger rocks(not the gravel anymore), and a new tall, thin stringy plant.  All properly cleaned as the directions said.  I put all the fish in there together, after the water temp was even.  The goldfish loved it!  They are swimming normally, seem to be having fun, not being over fed.  However, it had been a week, and my sucker fish just died.  Gave no signs of illness.  I was wondering if you have any ideas why, so I can avoid this in the future?  And perhaps some ideas of why the goldfish acted the way they did.

Answer
Hi Lisa,
 It sounds like the water went bad in the tank because of the excess food.  The trouble is that changing the water doesn't necessarily fix the problem.  While you need to change the water to get rid of all the toxins from excess food, doing so entirely disrupts the aquarium and kills all the beneficial bacterial as well as the harmful bacteria.  So, now you have a fish tank that is essentially brand new but with a bunch of fish in it.  The usual result of that is that that the fish get sick after a little while (which is what you saw) because the water chemistry is all out of whack.  

 Solutions:  The most obvious is of course to put the fish food on a higher shelf.   A less obvious solution is to have a larger aquarium.  The larger the tank the more natual buffering it has to these sorts of incidents -- basically there is more water to handle any sort of temporary problem.  This makes life much more stable and easier for the fish in the tank.

-- Ron
  rcoleman@cichlidresearch.com
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