50 Gallon Tank Weird Slime Issue


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I am at a loss, I'm hoping my tank isn't beyond saving. I will open with the fact that my axolotl is my first time attempting caring for a fish and I feel clueless. After a weekly water change, my tank went from clear to a hazy white color over the course of a week. I did of some research into what the issue was and learned I may have crashed my cycle by discarding a prefilter sponge I had on my hang on back filter. I only put it on there originally when my axie was small to prevent injury and thought I didn't need it any more.

So I tried not to worry and monitored water conditions for the next couple weeks hoping the tank would cycle and correct itself. After that time period I started to notice an almost booger like slimey stalagmite coming from my filter and no change to my tanks conditions. At this point I went to the local pet shop to seek advice, and was advised to have been doing 50-75% water changes every 2-3 days for the past month. When I went to change the water tonight, I noticed the attached pictures is what I'm dealing with.

It is now getting close to two months like this and I am so worried and woefully unequipped to know what I can do to clear this up. I don't know if my filter media needs to be replaced or if that would even accomplish anything. I don't know if whatever this slime is would infect my new media or crash my tank even more. I would greatly appreciate some advice on the correct course for trying to get my poor axolotls living conditions back to what it deserves.


Peter M

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2 years
Does the water still look like that after a month or two of water changes? And do you know what the parameters are?


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South Jersey
More than 10 years
Welcome to FishLore!

If your not 100% sure about the nitrogen cycle click on the words and you'll be taken to a page explaining it.

Do you have a test kit for testing the ammonia, nitrite, nitrate and pH levels? It is very important to have one, else you'll have no idea if you are cycled or not. I highly recommend the API Master Test Kit for Freshwater. Stay away for the test strips. Their low price makes them attractive, but they are notorious for being inaccurate. And if you can't trust your test results...why bother testing.

In a cycled tank, the bacteria that cycles your tank, lives in the filter media (it looks like in your case it's filter floss, but in some filters it is ceramic rings or noodles). You never want to change the floss unless it is absolutely disintegrating, because if you remove the floss you also remove the bacteria that cycle your tank. So you should just swish it out in some dirty tank water while doing your water change. (The chlorine in tap water will kill the bacteria in the floss, that's why you want to use old tank water).

In a cycled tank, your usually looking to do a water change every week. How large of a water change can be guided by your nitrate level. Ideally you'll want to keep nitrates under 20ppm at all times. Usually this means doing between 25% and 75% depending on your bioload. (The more ammonia, the more resultant nitrates).

If your tank is not cycled, I highly recommend you pick up a bottle of SeaChem Prime. Prime is a dechlorinator, like many other products, but what set's Prime apart from the others is that a standard dose of Prime will detox up to 1ppm of ammonia and/or nitrites.

Here's a link you may find helpful:

Best of luck!

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