smelly water

Question
I have had the 35 gallon tank for 6 years 2 fish being origanl residents ( black molly and algea eater)I have added a small fan tail recently.  I had to clean the tank thuroughly because I moved it near a window and it got over run with algea.  I cleaned the tank and changed probably 90% of the water.  Then added a calico fan tail. so that makes 4 fish.  Its got a 20-60 aqua clear filter.  not sure about the ammonia or nitrates but the ph was over 7.6.  the tap water is only slightly alkaline like 7.2.  15 % water change every 2 weeks but the cats drink out of the filter so it gets some added daily.   Anyway since i cleaned it it stinks like stagnent water in a pond would smell on a really hot day.  Now i realize the ph is very alkaline but always has been ...for 6 years but whats with the smell?  is it just cause i changed almost all the water?  I appreciate the help as it is in my bedroom and is very unpleasent

Answer
Hi Angela;

It's the fantails creating waste in the form of ammonia. They are messy guys that add a lot of waste even when small. The beneficial bacteria hasn't compensated yet by developing enough extra colonies to consume the extra ammonia.

Fantails are a fancy goldfish and they like cooler water too. Your other fish are tropicals so the goldfish will not do well over a long term period if the temperature is over 72f. They would do better in their own cool water 20 gallon or larger tank with good filtration and no heater. Here is a  link to a good web page about the basic needs of goldfish;

http://www.firsttankguide.net/goldfish.php

Watch out that the algae eater doesn't suck the sides of your fantails too. Watch for missing scales or sore spots. Goldfish produce a thicker slime coating than other fish do and some algae eaters find it tasty. Yuck! :-0

I hope things go okay...

At Your Service;
Chris Robbins