Betta fish lethargic and can't swim: Is a heater always necessary?
Updated On September 23rd, 2025
Pet's info: Fish | Unknown - Fish | Male | unneutered
I live in Hawaii and was told that I didn’t need a heater for my baby beta fish. I still find my fish to be very lethargic and unable to swim properly. What should I do.
2 Answers
Most Helpful Answer
Published on April 30th, 2018
Bettas are tropical fish and do best in water between 78 F and 80 F. A heater is typically required to maintain stable temperature. Rapid fluctuations in temp can be stressful. You should also check the water quality and chemistry. Poor water quality can cause the symptoms described. Filtration and regular partial water changes are necessary to keep a tank clean.
2Pet Parents found this answer helpful
Related Answers from Veterinarians
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Published on April 29th, 2017
That sounds perfect! Bettas, like many other tropical fish, have an ideal temperature range of 76-82 degrees. 20% water change every week is ideal as well. Please do not hesitate to contact us again on the forum or by requesting a consultation if you have any more questions or to discuss it any further.
1Pet Parents found this answer helpful
Health & Wellbeing
i recently got a beta fish, he swam around all the time and now he just lays around. The only time he gets up is when i feed it and when i turn the lights on, i guess the lights just startle him. I looked online and what i read suggested that i get a
Bettas are tropical fish and do best in water between 78F and 80F. Cold water will affect appetite and activity. It can also cause stress which may lead to illness. A submersible heater which a rheostat/thermostat control is recommended. Choose one based on the size of your tank. A thermometer is also recommended to confirm proper temperature.
Updated on September 24th, 2025
Health & Wellbeing
Hi, I have a Betta fish and it is very low on energy level these days and it is losing his color.
Bettas are tropical fish. They need warm water. They do best between 78F and 80F. Clean water is key in treating any infection. Check water chemistry using a home test kit or by submitting a water sample for testing. Aim for 0 ppm ammonia and nitrites with a 40ppm or less nitrate level. Perform partial water changes to stabilize chemistry and maintain water quality. Use only aged or conditioned water that is temperature matched to prevent stress or shock. A bit of aquarium salt (NOT table or Epsom salt) can be used as a general tonic to reduce stress, treat minor infection and aid in any recovery. Dissolve 1 teaspoon of salt per gallon of water in a cup of tank water and gently pour it into the tank. Treat for 10-14 days then reassess fin condition. More water changes can be done afterwards to reduce salinity.
Updated on September 24th, 2025
Health & Wellbeing
My fish is bloated near the head and he won't swim. He just floats at the top and his fins hardly ever move. He only eats his food when it begins to float to the bottom of the bowl. His fins are pitiful and dull. He won't interact or flare his fins a
Check water temperature and chemistry. Bettas do best between 78 F and 80 F. Unless the room is very warm, a small heater is typically required. Without a filter, frequent water changes are necessary to prevent elevated levels of ammonia, nitrites and nitrates. All can be toxic to fish at high levels. Use only aged or conditioned water that is temperature matched to prevent further stress or shock. Plain aquarium salt (NOT table salt) can be used as a general tonic, to reduce stress, to treat minor infection and to aid in recovery. Dissolve 1 teaspoon of salt in a cup of tank water and gently pour it into the tank. Perform daily water changes, using aquarium salt for 10-14 days. If there is no improvement, consider a broad spectrum antibiotic. You can find one in the aquarium section of the local pet or fish store. Follow label directions carefully.
Updated on September 24th, 2025
Health & Wellbeing
My pet betta has been pale and black for a long time and he leans on hi side and doesnt swim much
Check the water temperature. Low temps can affect activity in fish. Bettas do best in water that is between 78 F and 80 F. Check the water quality as well. High ammonia or nitrites can cause the symptoms you are describing. Perform a partial water change if necessary. Use aged or conditioned water that is temperature matched to prevent shock. Monitor water chemistry until ammonia and nitrite levels are 0 ppm (parts per million) and nitrates are 40 ppm or less. Constipation can also be a potential cause. After environmental parameters are corrected, fast him for 2-3 days. Resume feeding small bits of cooked shelled green peas until he is defecating normally. Transition back to a quality pellet afterwards.
Updated on September 24th, 2025
Health & Wellbeing
My baby beta fish has not been able to swim up lately, he stays at the very bottom of the tank and barely moves. He has trouble swimming and I found him almost floating vertically. Please help.
Check the water chemistry and temperature. Elevated ammonia or nitrites can be toxic and low temps can affect activity. Bettas do best between 78 F and 80 F. You can use a home test kit or submit a water sample for testing. Most pet stores will do this for free or for a small fee. Perform partial water changes, if indicated, to stabilize chemistry and maintain or improve water quality. Aim for 0 ppm ammonia and nitrites with nitrates at 40 ppm or less. If possible, turn don the filter flow so the little guy isn't pushed around by a strong current. Bettas prefer slow moving water. Lower the water level to make it easier for him to surface. Bettas are air breathers. Feed Micro Pellets or crush regular pellets so he can eat them. You can moisten pellets with a bit of garlic juice to stimulate his appetite.
Updated on September 24th, 2025
Health & Wellbeing
My male Betta fish isn’t moving
Check the water temperature. Bettas do best between 78F and 80F. Low temps can affect activity in fish. You may need a small submersible heater to maintain water temperature. Next, check water chemistry. You can do this with a home test kit or by submitting a water sample for testing. Most pet stores will do this for free or for a small fee. Confirm an absence (0ppm) of ammonia and nitrites with a nitrate level of 40ppm or less. Partial water changes may be indicated to stabilize chemistry and maintain water quality. Use only aged or conditioned water that is temperature matched to prevent stress or shock.
Updated on September 24th, 2025
Health & Wellbeing
I just got a betta fish yesterday. He was fine and swimming an hour ago but now he is at the bottom of the tank just kinda laying there and Hindi g in his cave. He is still alive just lathergic. I think he is dying. We put 8 drops of water conditione
Check the water chemistry and temperature. Use a home test kit or submit a water sample for testing. Most pet stores will do this for free or for a small fee. Aim for 0 ppm ammonia and nitrites with nitrates at 20 ppm or less. Perform partial water changes, no more than 30% total volume at a time, to stabilize chemistry and improve water quality. Use only aged or conditioned water that is temperature matched to prevent stress or shock. Bettas are tropical fish and do best between 78 F and 80 F. You may need a small, submersible water heater to maintain temperature. Feed either the pellets or the bloodworms at one meal. Offering both is too much and he likely won't eat it all. Any uneaten food will rot in the tank and foul the water.
Updated on September 24th, 2025
Health & Wellbeing
My fish is super inactive. It’s a rose tail or rose petal betta. He just sits at the bottom. How do I help him?
Check the water temperature. Bettas are tropical fish and do best between 78F and 80F. Low temps can affect activity in fish. If temperature is normal, check the water chemistry and perform a water change if necessary. Use only aged or conditioned water that is temperature matched to prevent stress or shock.
Updated on September 24th, 2025
Health & Wellbeing
Hello,I have a betta which used to be very active and responsive but since almost 3 weeks it is very inactive.It stays at bottom or top.Do not eat much.The color has also faded.Please help
Check the water temperature. Low temps can affect appetite and activity in fish. Bettas thrive between 78 F (25.5C) and 80 F (26.6C). A heater is required in most tanks. Test the water also. Use a home test kit or submit a sample for testing. Most pet or fish stores will do this for free or for a nominal fee. High ammonia or nitrite levels can cause stress or illness. Partial water changes should be done regularly to maintain water quality if a filter is not used. Aged or conditioned water should be used instead of plain tap water. It should be temperature matched as well to prevent stress or shock.
Updated on September 24th, 2025
Health & Wellbeing
My beta fish is lying on its side at the bottom of the tank, he hasn’t moved much or at all for a couple of days. He has short jolts of energy but ends up sinking. Water has been changed, and filtration is on. What might be the problem?
Check the water temperature. Bettas do best between 78 F and 80 F. You should also lower the water level to make it easier for him to reach the surface. Test the water or submit a water sample for testing to rule out elevated ammonia, nitrite or nitrate levels. Most pet stores will do this for free or for a small fee. Perform partial water changes, no more than 30% daily, to stabilize chemistry if indicated. use only aged or conditioned water that is temperature matched to prevent further stress or shock. Soaking pellets in garlic juice may stimulate his appetite and provide an immune system boost.
Updated on September 24th, 2025
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