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MD wrote,

First, I want to tell you how impressed I am with your website! Thank you so much for providing such a rich resource to betta enthusiasts! I am concerned about my betta fish, Nino. I have had him for three months and he has been a great companion in my study, where I spend most of my time. He was in a 5 gallon aquarium, with no filter and no heater, and was really thriving. As winter is approaching, I wanted to provide him with a heater and a filter to circulate water. Considering how active he was — swimming back and forth through his tank most of the day — I decided to switch him to a 10 gallon tank. I was as careful as possible in the transition — I “seeded” the gravel from his old tank to his new environment + I mixed the new water with the water from his old tank and made sure it was the same temperature.Since Nino moved to his new aquarium, he has been increasingly less active, and this morning, he remains still at the surface of the water most of the time. He still eats. I should specify that the temperature in his aquarium has been pretty steady at 74-76 F since I got him. I have put the heater and filter in place, but I have not started them yet (I thought I should first give Nino a chance to get used to his new tank for a few days). The filter (duetto mini) does contain a very small charcoal cartridge (could that contaminate the water if not in use?). I have been using spring water from the time I got Nino and have been doing weekly water change. I have tested his water yesterday and today (with API Master test kit) and the reading are good : ammonia between 0 and .25, nitrite: 0; nitrate: 5.0. The pH is high — 8.0 — but I have been using the same spring water, and noticed high readings in the past as well.

Nino looked perfectly healthy and happy before the transition and I feel pretty bad seeing him still, with very little reaction to stimuli and noticing his condition getting progressively worse since yesterday. I wonder if I should try to put him back in his smaller tank or if I should I make a water change?… I’m very confused and worried!

I would really appreciate your suggestions!

Moving into a new aquarium can be stressful at first even though it’ll be better in the long run. It is not at all unusual for Bettas show signs of stress including sluggishness, loss of appetite or dull coloration for example. Fish are incredibly in-tuned with their environment and can detect even minor changes in water chemistry, especially pH.

You will want to be sure that the new tank doesn’t have any soap or detergent residue, that the new water has the same parameters as the old (which you have done) and that any necessary water additives have been added. (Dechlorinator if necessary). If these precautions have been taken then it’s likely your fish just needs some time to adjust.

Adding plants (real or silk) and hiding places will help your fish to feel more secure while he gets used to his new territory. Also many aquarists recommend keeping the lights off or surrounding the aquarium with a towel for a day or two to help your Betta feel safe and protected.

I agree that keeping the filter off while your Betta is showing signs of stress is a good idea. Just be careful not to overfeed him during this time and if you detect any ammonia or nitrite you will want to turn on that filter to keep these toxins at bay. Regarding your question about charcoal, I don’t believe it is causing additional stress. Charcoal is generally safe for Bettas but if you are worried you could always remove the cartridge until you are ready to run the filter.

A ten gallon aquarium makes a great home for a Betta. Give it a few days at least to allow your fish to adjust. In most cases they will be back to normal within a week.

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Reader Interactions


  1. Bee says:

    Hi! I love your site and have tried to find a way to email you with NO luck concerning some questions.. 🙁 Where is a contact address? When I click on the link to your Nippyfish blog, it demands that I create my OWN blog, of which I have zero interest. You can email me at luna-tuna@msn.com and then delete my address. Looking forward to a way to reach you and thanks so much for your great and technical information.

  2. Christie says:

    Hi Bee,
    The best way to reach me is via email which is listed is the “ABOUT ME” section at the right of the page. The email address is betta[at]nippyfish.net
    I try to answer as many emails as possible and do get to the majority of them however I receive so many each day I can’t get to every single one. Still please do write in as I love hearing from readers and want to answer as many questions as possible. I also strongly suggest doing a search for your question in the “SEARCH THIS BLOG” box on the right of your screen. There are hundreds of questions answered and many can be found with a quick search.
    I look forward to hearing from you.

  3. Anonymous says:

    My betta lives in a 5 gallon tank. The tank has a heater but no filter. My betta has lived in the tank for about a week. Although the temperature the heater makes the tank is a little different than the temperature I set it for, my betta is nice and active. Should I put in a filter?

  4. Jessi says:

    You don’t need a filter with bettas, since they have laybrinth organs. If you want a filter to keep the water cleaner longer, i suggest a bubbler-powered filter. They are easy to use, effective, and not a problem with the fish that don’t do well with any currents. Please don’t forget to clean the water at least every other week though! My sister seems to think that she doesn’t have to, and she’s lost too many wonderful fish that way 🙁

  5. Anonymous says:

    Hi, I have a male and a female Betta fish and I would like to breed them, but when I put the female, who we have had for awhile and my new male Betta’s tail fins are all ripped and torn. I have taken the female out, since we have to tanks. But I’m still worried about the fin damage. What do I need to do? [=-C] My name is Connor and if any one can help please reply on the site, thank you =-)

  6. Anonymous says:

    hey, it’s me again. I put the male in the new tank first then waited a day and put the female in. Then I saw the female had an egg sticking out of her. Now when I went to sleep I woke up the next day looked in the tank and saw that the male had his tail fins torn up. I had a male Betta before so i am confused on why the fins are torn so i need help thanks

  7. GinaM says:

    Anon, your betta had his fins torn up because the female probably attacked him.
    You shouldn’t put a female in with a male betta, unless you’re going to mate them.

  8. Abby says:

    Hi, i have a twenty gallon tank (i don’t think that matters in this case) but every thing is perfectly fine in my tank. however my fish are constantly hungry 24/7 ecspecially the female betta i have. i feed them three times a day and they are still hungry. why is this?

  9. debbie bayles says:

    I’ve had Johnny (Betta) almost 3yrs. Moved him into a gallon & half glass vase from a one gallon plastic vase. He was always spunkie and couldn’t wait until feeding time. Its been over a wk now and he stopped eating! Tried different food, what should I do? I’m just torn apart about this, we’ve been through a lot with Johnny and don’t want to lose him!! Please help

  10. Brandi McMullen says:

    Thank you for this article it really helped me figure out why my new betta Tatsuya is acting so lethargic. He’s in a new 5 gallon and He won’t even eat yet. I’m not sure whether to wait it out and still feed him pellets or get him blood worms? What food would you recommend?

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