Fish Died suddenly

Question
I have a 150 gallon freshwater aquarium with a large (I forgot what it is called)filter that sits below the tank and two overflows (on on each end).  I have bubbler bar.  I have two oscars (each about 5 inches), five red-barbed silver dollars (each about four inches), a large plecostomos, a 3 inch catfish, a 3 inch jack dempsey, and (I had) 4 bumble bee ciclids added about one month ago.  My aquarium maintenance guy came last thursday and did his water change.  He is telling me that I overstocked my aquarium.  All the people that I am talking to otherwise say that it is just that he is not monitoring the water quality and maintaining it properly.  anyway, within three days of his coming and cleaning and changing Approx 25% of the water, 3 of the four bumble bees died.  I have heard that one inch per gallon should work.  Oh... by the way, even with the type of fish I have, there is little or no agression evident.  I feed only prepared food... no live.

Answer
Hi Bruce

I pulled your question from our question pool. I apologize for the delay in answering.

Your aquarium maintenance guy is absolutely correct, you overstocked your aquarium. It isn't just one inch of fish per gallon of water. That rule is based on the size the fish will be as adults, not the size they are when you buy them. This rule works with small fish like Gouramis, Barbs, Tetras, Mollies etc. With the massive fish you have, you also have to determine volume. (L x W) One Oscar needs a MINIMUM of 40 gallons to himself. Two Oscars need 80 gallons. Then you added a Jack Dempsey who also needs 40 gallons of water. So you have 120 gallons with just those 3 fish. Then you have 5 Silver Dollars which adds another 35 gallons worth of fish. That's 155 gallons of fish already and that is without the Pleco and the Catfish who are easily adding another 30 gallons.

Now, overstocking is not what killed the Bumblebee Bee Cichlids. They died of improper water quality. Bumble Bees are an African Rift Lake Cichlid from Lake Malawi. Their water chemistry requirements are completely different from Oscars, Jack Dempseys and Silver Dollars who are all from South America. African Cichlids need hard water, pH of 8.0-9.0 A pH usually only obtained by using pH buffers or a substrate designed for African Cichlids. South American Cichlids need a neutral pH of 7.0

It's always a good idea to research fish and their requirements prior to purchasing them. Doing so will save yourself a lot of heartache and headaches, as well as unnecessary death to the fish.

Hope this helps you, good luck!

Richard