Old Tank Syndrome?

Question
Hello!  I've recently added some new fish to an existing 30 gallon freshewater aquarium.  We had one new fish loss (Bloated Mollie), and one existing fish (Shark) soon died.  I did a 50% water change, thinking that might be the cause (it had been a while).  

After the water change, another Shark died.  I took a water sample to our local fish store and the Nitrate levels were WAAAAY out of whack.  They advised me to do another 50-75% water change, which I did.

I bought my own testing kit (5-in-1: Nitrate, Nitrite, pH, Hardness and Alkalinity) and have tested the water 3 days in a row since doing the 2nd water change.  The nitrates are still REALLY high.  pH is teetering on the high side and hardness is "very hard" but we don't have a water softener so that doesn't surprise me.  ALkalinity was in the good range.

I've been doing a lot of research and it sounds like we have "old tank syndrome".  I feel extremely guilty that this problem was caused by me but I want to do as much as I can to fix the situation, as quickly as I can because I don't want the fish to suffer any more than they have to.

I'll be doing more water changes, as I've read I should.  I've also found information on filter media, but the descriptions I've seen are not clear in how to use it.  I have a Power Filter.  Is this something I would use in place of the activated charcoal for a while?  Or is it in addition to the charcoal in the filter bag?  Do I sprinkle it into the tank?

Is there anything else I can do, to change the nitrate levels quickly?

Thanks SOOOOO MUCH for your help!
Mary
Watertown, WI

Answer
Hi Mary;

Nitrate is very low in toxicity and is the end result of the filtering system. It is not going to cause the deaths you described. It will cause fish to be weaker than they should and they usually can't breed, but not deaths like that. I hate to blame fish stores for causing problems like this, because many get blamed when they shouldn't, but I think that is exactly what happened. The new fish introduced something that the older ones were not accustomed to fighting. The shark died from not being able to fight it. The second shark may have died from the water change as well as weakness from being sick. That much changed at once can cause death from shock. Especially after so long without one. Raise the temperature slowly to 80 or 82 degrees for 2 weeks to help the fishes' metabolism and immune systems fight whatever may have been introduced. The heat also weakens or kills parasites, fungus and bacteria. They probably don't need medication. Always avoid that if you can.

Don't do anything to the filter. The only solutions for high nitrates is regular water changes and live plants. Live plants use it as fertilizer. That's why natural outdoor environments don't have a problem with nitrates. There are plants and other natural things to help it dissipate or be consumed. It is there for a purpose and it is being used for that purpose out there. Our "closed system" aquariums don't have the benefit of that action. Replace 25% of the water every day for the next 4 days and add some live plants. The fish will like them and be healthier with the water changes too. If you have other livebearers like mollies, it is essential for their health to have frequent water changes. They can't tolerate dirty water and will get sick easily.

After the cirsis is over, make 25% water changes every week and don't overfeed the fish. Overfeeding is a major contributor to nitrates. The fish must fully consume every speck of food from the tank within 5 minutes. Any leftovers pollute the tank.

How many fish and what sizes do you have in the tank? (I'm hoping it isn't overpopulated...)

Followups Welcome

At Your Service;
Chris Robbins

Come on over and join us on the freshwater fish forum at About.com to get even more information too;
http://freshaquarium.about.com/od/questionsanswers/a/naavigateforum.htm

My member name is ChrisR62. See You There!