The 3 Most Common Aquarium Cleaning Mistakes

Sometimes you are much better off knowing what NOT to do rather knowing what you should do.  Aquarium cleaning may be one of those things.  There are some very simple things that seem harmless but could have serious effects on your tank.

Using Bleach or Cleaners

This aquarium cleaning mishap could have disastrous effects on your tank.  This really doesn’t seem like a bad idea in theory.  If you want to really get something clean, you use bleach right?  Not in your fish tank.  Even trace amounts of bleach and other cleaners left behind in your tank or on your decorations can seriously harm your fish.  Just use plain water and some hard work to clean your tank.  That’s all you need to get the job done.

Rinsing Your Aquarium Gravel

Completely cleaning your aquarium gravel also seems like a good idea.  After all, your gravel catches all of your aquarium waste making it the one of the dirtiest parts of your tank.  So what could be wrong with that?  Your gravel is one of the greatest breeding grounds for all of those good bacteria that make up your bio-filter.  Because of this it’s best to leave the gravel in place when you’re cleaning your fish tank.  The best way to clean your gravel is just siphon up the major debris off the bottom.  This keeps that bio-filter in tact and keeps your fish happy during your aquarium cleaning.

Cleaning Too Much At Once

This aquarium cleaning mistake is similar to the one above in that it is related to your tanks bio-filtration.  You wouldn’t think you could really clean too much, but you can.  Your tanks good bacteria are growing all throughout your tank once it’s established.  On your tank walls, plants, decorations, filter media, gravel, and even in the water.  If you clean all of these things at once your bio-filter looses its effectiveness.  One solution is to clean things in stages.  One week you could do a partial water change, and clean the glass.  The next week you could clean everything else.  Another solution with regard to the filter media is to just rinse it in your tank water rather than replace it.  This keeps the bacteria in your tank and sufficiently rinses the media.

What sort of cleaning issues have you had?

, , ,

37 Responses to The 3 Most Common Aquarium Cleaning Mistakes

  1. Jolene August 11, 2007 at 3:55 pm #

    I already knew all of this cause ive had many goldfish, 2 guppies, 2 male bettas, and currently have 3 goldfish. I always clean out like 1/3 of the water.

  2. jolene August 11, 2007 at 3:57 pm #

    I normally clean out 1/3 of the water and little of the rocks. I only have a 1 gallon tank so its easy to clean. I have ahd many fish including 2 male bettas, guppies, and have three goldfish currently.

  3. Ruby August 19, 2007 at 9:32 pm #

    my tank had clear water and you do a 20% water change the water gets cloudy and in few days its get worse. 🙁

  4. Eric August 31, 2007 at 9:40 pm #

    Hello Ruby,

    Take a look here.
    That should settle a few days after the water change. You’ll also what to make sure you are using a gravel vacume when you do your water changes.

  5. Kim Mosher March 6, 2008 at 1:01 pm #

    Why after I used triple sulfate and did the water changes as shown(I had a couple sick fish and it helped them) Why is the water now red?

  6. j.gray March 8, 2008 at 1:22 pm #

    black mold in fish tank how to get ride of, I have tried every product – all mt fish are dead now and still can’t remove thev black mold!!!!

  7. Eric March 10, 2008 at 8:07 pm #

    Don’t worry about it. It’s no big deal. Many treatments have a coloring affect. After a number of water changes it will quickly dilute and disappear.

  8. Eric March 10, 2008 at 8:14 pm #


    Black mold is a tough one. I don’t have any great suggestions other than get a brush and scrub it all down. It takes some work but there’s not all that better a solution.

  9. Darci March 23, 2008 at 11:30 am #

    My fish have slowed down….Two of them are just kinda hanging around in one area, not moving much. Are they sick? What should I do?

  10. Eric March 25, 2008 at 8:13 pm #

    Hi Darci,
    Sounds like they are stressed from something. They might not be sick from disease though. You’ll want to look for other signs of disease before guessing at treatments. You should also test the water to look for signs of stressful water problems.

  11. Kathie Kennedy April 6, 2008 at 9:24 am #

    I now have a 10 gallon tank and want to change it to a 20 gallon. Can you tell me a safe way to move my fish.

    Thank you.

  12. Eric April 8, 2008 at 8:49 pm #

    Hi Kathie,
    Just use a net of course to physically move them but here are some other tips. Use your same filter pad if you can. Use the water and gravel from your 10 gal as well. This basically transfers your good bacteria over to the new and you don’t have to worry about cycling. Take a look here:

  13. Leslie May 4, 2008 at 1:46 pm #

    Hi Eric,

    I have a 5 gallon tank with one goldfish in it. The tank is several years old, and I haven’t really had any problems until recently. For the last couple of months I have been experiencing cloudy water. I have a bio-wheel filter system that seems to have worked great until now. I have tried small water changes, large water changes, carbon filter changes, addition of water conditioner etc. I typically do a 20% water change every week, cleaning the gravel with a vacuum and adding aquarium salts and water conditioner back. I think that I have had bacterial bloom, but I have not been able to get rid of it! I feed the goldfish one half of those frozen brine shrimp or ’emerald entree’ pieces, twice per day. Do you have any suggestions on how to get this under control? Thanks so much!!

  14. Eric May 4, 2008 at 3:29 pm #

    Hi There Leslie,
    You need to do two things. Stop the source and replace the cloudy water with clean. Take a look here for tips.
    The root is probably overfeeding or direct sunlight. These are just the most common. To get rid of the cloudy water if it’s bad, you’ll want to do 50% water changes every two days until it’s clear. Once you get there and stop the root of the problem, you’ll be in the clear, literally.

  15. kevin May 6, 2008 at 12:06 am #

    I bought an angelfish and it died in less than 24 hours. I checked the water and it was within the right range with a PH of 7.0 and no ammonia. I then got another one to replace the one I lost. I have no idea why this happened . The other fish in the tank are Molloies and Tetras (neon). I would appreicate it if you could help me. I would like to get another but not if they just keep dying.

  16. Eric May 7, 2008 at 9:35 pm #

    Hi Kevin,
    Could your Nitrates be high? Did you buy them the same place? Could have both been sick in some way. Temperature way off? You really just have to run through all the other possibilities. Without anything jumping out, it could be just about anything.

  17. marian May 20, 2008 at 5:54 pm #

    For months, I have had a bad ammonia problem. Usually at 5, instead of 0. I know I have too many goldfish in tank, but even with 1/3 water changes every two days, and syphoning the gravel, the ammonia is still as bad as before. I’ve tried ammo-lock and waste control, but no better. How can I get ammonia level in a good range, without having to get rid of some fish, as I don’t have room for another tank. I have seven small goldfish in a 10 gallon tank. Plus two small catfish.

  18. kevin May 20, 2008 at 8:27 pm #

    thank you eric for trying to help me but my female mollie was killing them guess she does not like them but i got 2 rainbow fish and she likes them

  19. victor May 22, 2008 at 2:40 pm #

    my fish keep dying lil by lil! what am i doing wrong?

  20. Eric May 27, 2008 at 6:18 am #

    Hi Marian,
    An ammonia reading of 5 is very high. I am surprised you are not loosing fish. They are stressed. You are probably going to have to get rid of some fish. Your local fish store will probably take them if you have no other place. A couple of quick checks though. Make sure you are cleaning/changing your filter pad regularly. Also make sure you are digging into your gravel when cleaning. You should be digging to the bottom and seeing the black puff of waste. Do this for every inch of the bottom and you should really see some improvement with water changes that often. You might just be leaving the waste in those other places.

  21. Eric May 27, 2008 at 6:22 am #

    Hi Victor,
    Need a little more detail but this is a starting point.

    Grab some test strips and start to look for a cause.

  22. marian May 27, 2008 at 6:45 am #

    Eric: Hi, Eric! Thanks for the info. I was told I am cleaning the gravel too often, and to do it only once a week. But, to stir up the gravel, daily, to get the dirt into the filter. I had the ammonia level at 0 for a while, until I made the mistake of cleaning all of the filter parts at one time. From then of, the level was 5. I think I am also using too many chemicals, too often, and destroying the bacterial bed. What do you think?


  23. marian May 27, 2008 at 7:11 am #

    Eric: Hi, again! I just stirred up the gravel, right to the bottom of the tank, and the black puff of dirt came out of it. I hadn’t been going deep enough all this time, in cleaning the gravel. I also did a 20% water change to get rid of some of the cloudy dark water, plus put in some accu-clear. Perhaps, this is where the ammonia is coming from – not cleaning the gravel thoroughly enough. Thanks for the tips!!


  24. miss zoe May 28, 2008 at 5:53 pm #

    i had 6 goldfishes for for 1 and a half wks they all died do to ick and im planning on getting some more and i was wondering how to prevent it from happening again and how to make sure my tank is ick-free,this is my first exprience with owning a fish

  25. Eric May 29, 2008 at 8:44 pm #

    Great Marian! You should have it under control quickly. It is true that cleaning so often isn’t good for you bio-filter. The only problem is that it’s really the only way to keep your ammonia levels under control when it’s super high. The benefit outweighs the problems to keep the changes up. You can slow things down when things level out. Good luck!

  26. Eric May 29, 2008 at 8:57 pm #

    Miss Zoe,
    Just clean the tank and everything thoroughly with water. You really can’t do anything to prevent it if they come with Ich from the shop. I would buy from a different store and look for signs before taking them home.

    Also, take a look here for starter tips. Start with 1 or 2 fish rather than many, is probably the most important tip.

  27. marian June 6, 2008 at 6:57 am #

    I’m writing about my ammonia problem, again. I make sure I don’t overfeed fish; I stir up the gravel to the bottom, and all over, once a day, to get debris out of it; the water is crystal clear; yet, I still have a high ammonia reading = 5. Two days ago, I put Ammo-Lock in tank, but no difference on read-out. Fish don’t appear to be stressed – they must be used to it, by now. This has been going on for many months, now. I don’t know what else to do. I know I have too many goldfish in tank, but, even so, water is so clear since stirring up gravel, daily. It seems almost impossible that something could be wrong with the water, still. I don’t have a second tank, to put some of the fish in; and local pet store won’t take them. Any other suggestions, would be appreciated.

  28. Eric June 8, 2008 at 2:48 pm #

    The only other thing you can do is keep up on big water changes very frequently. That’s the only safe way without removing some fish. I know it get to be a pain every day or two but it’s the only way if you are way overstocked.

  29. marian June 9, 2008 at 6:15 am #

    Eric: Not long ago, I did frequent water changes = 30% approx., but no change in Ammonia levels. I changed water every other day, for many weeks. I bought too many goldfish as I didn’t take into account how much they would grow. I have a ten gallon tank, with seven goldfish and two catfish in it. All are under two inches, at this time. I was informed that I should only have one or two goldfish in this size of tank.

  30. Eric June 9, 2008 at 8:50 pm #

    Yeah, Goldfish typically grow to about 6″. They’ve been known to grow much bigger. 1-2 max would be suggested for a 10 gallon.

  31. marian June 10, 2008 at 5:56 am #

    Eric! Guess what! I checked the ammonia level this a.m., and it reads 0.5!! Yesterday, it was still 5.0. Yesterday, I lightly rinsed out my filter parts, and canisters, and changed the Foam filters, and now, to-day, the readings are almost back to 0. Thanks for all your help, especially about stirring up the gravel, daily, all over the place. I think that really did it. I only hope and pray it stays this way, now.

  32. Eric June 10, 2008 at 8:41 pm #

    That’s great to hear Marian! Thanks for circling back around.

  33. Scott July 26, 2008 at 7:21 pm #

    Hi Eric, Have just found your website – what a great job you’ve done!! When vacuuming the gravel, should you just go over the top or push the vacuum down into the gravel? I’ve always done the later, but still consider myself a newbie so don’t really know the best way?? Ive got a 3′ tropical tank that is just cycling back up after 12 months of being ignored!

  34. marian July 27, 2008 at 6:21 am #

    Scott: I did what Eric suggested, which was stir up the gravel, daily, all over, and syphon the gravel once a week. When syphoning the gravel, you don’t really get in all the corners, etc., but stirring up the gravel with your fingers, gets all the corners, and under plants, rocks, etc.. Now, I don’t have any problems with the water, even though my tank is overstocked.

  35. Eric July 28, 2008 at 6:03 am #

    Hey Scott,
    Thanks! Like Marian said, you’ll want to get it stirred up by digging down in it when siphoning. A lot of the waste is deep in there. You’ll see a black puff of waste which is a good sign of getting the stuff you want out.

  36. Sam July 28, 2008 at 1:34 pm #

    We’ve inherited a very nice 130 Gal. tank setup with a few fish that are doing quite well.
    I need to move the tank to another location. We’ve had, iguess what you call an Algae Bloom?
    It’s everywhere!
    We have been told to pull all the fish, gravel, and fake limbs out and clean with Vinegar to kill the Algae. We have also bought a new canister filter #1200 Cascade, to replace the old siphon system.
    Will it be best to save some of the water that is in the tank now, to help estabnlish the bacteria needed, or should we just hook up the new filter so we start some of the bacteria growth in it, prior to moving the tank?

  37. Eric July 30, 2008 at 7:30 pm #

    Hi Sam,
    Adding your new filter to your old water would be the best way to grab some of that bacteria. Cleaning everything in that way isn’t really the best idea though. If you work on the cause, you can get it under control without destroying your bio filter. Here’s a popular article about algae that should give you some ideas on cause & treatment