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Betta Fish: New fish owner – tank smells bad, filter clogged, black slime found. Please help 😞


Hi everyone, I’m a new fish owner and new betta owner, so please be kind – I’m genuinely trying to learn and do better.

I’m having a sudden issue with my tank and I’m pretty worried.

Tank details:

• 45-liter tank

• 1 betta

• 2 plecos

• 4 corydoras

• Hang-on-back filter (I know now it’s too small – I was already planning to upgrade it on Wednesday)

Timeline:

• Saturday:

• Did a \~30% water change

• Cleaned the filter fully using old tank water

• Noticed some red leaf plants were dying, so I removed them

• Plants had translucent stringy material on them and debris floating around

• Tank had a slightly damp smell, like wet wood

• Today (Tuesday):

• Came home from work and the tank smelled really bad

• Filter was barely flowing and looked clogged (see photo)

• Water looked murky/unhealthy

I panicked and:

• Did a 50% water change

• Removed all plants

• Found slimy debris and black slime-looking material while pulling plants out

I haven’t added any chemicals besides dechlorinator. No fish deaths so far, but I’m really worried.

Questions:

1.  What could the black slime and translucent stringy stuff be?

2.  Did cleaning the filter + dying plants crash my cycle?

3.  Is my tank overstocked for 45L?

4.  What should I do right now to keep my fish safe?

5.  Should I leave the filter media alone until I upgrade, or replace it?

I know I’ve made mistakes, and I’m trying to correct them. Any advice, guidance, or reassurance would really mean a lot. Thank you 🙏

https://i.redd.it/6ltzf1anjwfg1.jpeg

Posted by FirefighterSavings61

7 Comments

  1. Brilliant_Ask852 on

    i’m not seeing you mention anything about water parameters or conditioning — please answer the auto mod questions too!

  2. dcl415 on

    And what type of plecos? Do not forget the parameter please and also did you CYCLE the aquarium before adding that many fish?

  3. FirefighterSavings61 on

    Tank size: 45 liter tank
    Heater/filter: heater no cuz I live in Asia (specifically south east Asia Singapore temps usually range from 30-33 degrees/ filter yes
    Tank temp around 25 degree
    Water parameters the only thing i hve a test for is my ph as the guy at the shop said that was the only one I needed. But after joining this thread I figured it wasn’t enough but am really tight on funds to get it right now. Possibly could get it tomorrow if my pay is in. In my county test for drop test is 25$ per pop and I am left with $100 for the rest of this month

    Water changes weekly 20% with siphon which again is what the fish shop guy told me was enough

    This tank is 3 weeks old but I had the fish since early Jan

    Tank mates as listed in the post

    Decorations and plants as shown in this picture

  4. Automatic-Standard32 on

    So first I would say ( and I know you plan to on Wednesday ) but as soon as you can replace that filter to a larger one the better so try your best to get that done tomorrow . I do strongly encourage you to get a water testing kit if you don’t have one already or at the very least take some water in to your local fish store for testing if you need some time to buy your own kit . As far as overstocking the beta is great in there an the Cory’s should be okay too but plecos produce soo soo much waste and I think pet stores don’t really tell you the truth about these when you buy them . I think they’re advertised like they’re doing to be super helpful but honestly they’re poop machines which is definitely going to make for bad water perimeters with the size tank you have . I also just wanted to ask how long this tank has been set up and see if it was cycled prior to the addition of fish ?

  5. Brilliant_Ask852 on

    so it sounds like you probably didn’t cycle your tank before adding your fish which means that you need to be doing daily water changes until your tank has cycled and complete a fish in cycle. unfortunately you won’t know unless you can test for ammonia and nitrites and nitrates (the elements of the cycle).

    that’s a huge bioload for a big uncycled tank so I imagine that’s a huge part of the issue.

    fish stores owners seem like we should be able to trust them but sadly we cannot most of the time .

    your plants might be starting to melt and algae starting to form as well depending on the light set up you have.

  6. RightingArm on

    I highly recommend replacing your filter media with something permanent. The main purpose of filter media should be to host de-nitrifying bacteria. I recommend a cheap block of open cell foam. When it gets clogged, just give it a rinse and a squeeze under some water to remove excess material. Disposable filter cartridges are a scam, because each time you replace them, you lose all the useful bacteria in the filter. You also appear to be experiencing an bacterial bloom in the tank. It’s possible that your tap water contains a nitrogen source. Others might disagree, but I think maybe you should stop doing water changes because you may be feeding the bacteria. I recommend adding floating plants, or houseplants with roots in the water. Either way, the betta will appreciate the shade, and the plants will reduce the nitrogen in the water. One way to do this is to take the top off the filter, and plant lucky bamboo or pothos or spider plants directly into a foam block.

  7. FusRoDahMa on

    Bad smell is the decaying plant matter. Honestly once you get a bigger filter, it should improve your tank parameters immensely!

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