Expert: Richard Hight - 10/22/2009

Question
I recently set up a 10 gallon tank in my classroom. I let the tank run for 4 days and then introduced 3 tiger barbs (the pet store suggested this number since they are schooling fish). Everything was fine for a week or two, and then two died within a few days of each other.  I introduced two mollies. (I now realize that I shouldn't have introduced more fish, but the pet store didn't tell me that at the time). The third tiger barb died a few days later. I took the water to ANOTHER pet store to be tested. They told me about the cycling process and that my tank was still in the process and I just had to hope for the best for the mollies. With a week or a week and half, both mollies died. I left the filter and heater running on the tank for two weeks, did a 20% water change,  and got  the water tested again. This time, I was told it was fine. I bought two swordtails and introduced them last Monday. When I came back to school this Monday, one had died. The second died today (Wednesday). It looked like it had tiny white bubbles all over it and the tail looked like it was partly eaten away. I'm at a complete loss and totally frustrated and think I am cursed! Should I clean the whole tank (I can see some dark green/black algae on the plants and gravel) and start again or just give up?

Answer
Hi Gayle

I doubt you are cursed ;-) You simply added too many fish at once, and the fish you added were not the hardiest fish for cycling a tank.

I'm assuming at the current time there are no fish in the tank. What you should do is simply start over so to speak. Drain 100% of the water, replace the carbon cartridge in the filter. I say drain 100% of the water to remove any toxins that are currently in the tank from fish wastes, decay from the dead fish etc. Use a gravelvac to siphon the gravel. The algae you are seeing is common in new tanks and nothing to worry about, it can be cleaned off of the plants using an old toothbrush. Refill the tank with fresh water, add your water conditioner and let the temperature stabilize at 78°. Then add 2 Whiteclouds. Let the 2 Whiteclouds cycle the tank for 4-6 weeks then have your water tested.

At that time, you should be able to add one or two small fish, but then your tank will be at capacity. I wouldn't choose schooling fish for a 10 gallon. They are too small for schoolers.

Hope this helps, good luck!

Richard