My betta died. How to safely reuse tank, moss ball, and snail for new fish?

Thanks for using Petco Pet Education Center, formerly Petcoach! I am so sorry to hear about the passing of Norman. If the Betta tank is currently empty, I would suggest changing the gravel and cleaning it very well before putting another fish in it. Make sure to change the water regularly as this is often the cause of issues with Betta fish. Best of luck!

I recommend to start with having the water tested. Many times this is offered by the pet store. If all the fish have passed away, the culprit is most often poor water quality, a disease or the tank not being properly maintained for the species of fish. I do not recommend to get more fish until you know the water conditions are correct and that you know the environment (temperature...etc) is appropriate for the species of fish you want to have. I hope this helps.

Ideally, you want to wait at least 4-6 weeks for the tank to properly cycle regardless of size. Bettas are quite hardy and adaptable, so as long as water chemistry and temperature are good then you can probably add him now since you have everything set up. When testing water chemistry, aim for an absence (0 ppm) of ammonia and nitrites with nitrates at 20ppm or less. Water temp should be between 78 F and 80 F. A small filter and submersible water heater should be used. You will still need to perform partial water changes to stabilize chemistry and/or to maintain water quality. Use only conditioned water that is temperature matched to prevent stress or shock.

If you set up your tank and added Cola the same day, it is likely you are having water chemistry issues in addition to a fungal infection. Tanks should be set up and run for about 4 weeks before adding fish. This allows the tank to cycle. This means beneficial bacteria will populate the filter and substrate. It is important because they rid the tank of toxins such as ammomnia and nitrites. Since he is in the tanlk already, you can use a quick start product to jump start the nitrogen cycle. You can purchase this at the pet store. You will also need an antifungal medication. Follow label directions carefully. Make sure water temp is between 78 and 82 F and use a low flow filter to prevent a strong current. Partial water changes (no more than 30%) may be necessary to reduce ammonia and nitrite levels until the tank has cycled. Used aged or conditioned water that is temperature matched.

If you put an Oscar in with your Tetras, they will be harassed and eventually eaten. Use a home test kit or submit a water sample for testing to check chemistry. Aim for 0 ppm ammonia and nitrites with a nitrate level of 20ppm or less. It can be slightly higher if you have live plants. If there is still ammonia present, the tank is still cycling. The cloudiness may be micro-bubbles which will eventually resolve or it could be a bacterial bloom which will also resolve once the tank has cycled.

He is "old" for a Betta. Check the water chemistry and temperature. You can use a home test kit or submit a water sample for testing. The local Petco may do this for free or for a small fee. Aim for an absence (0 ppm) of ammonia and nitrites with nitrates at 20ppm or less. Perform partial water changes to stabilize chemistry and/or to improve water quality. Use only conditioned water that is temperature matched to prevent stress or shock. Bettas do best between 78 F and 80 F. The cloudy eyes may be due to infection. Maintaining pristine water quality will help, but you may need a broad spectrum antibiotic as well. Look in the aquarium section of the local Petco for medication. Follow label directions carefully and remove the carbon filter insert during treatment if indicated. Even with treatment, there may be permanent damage to the eyes if the condition has been chronic. The "laying down" is sometimes seen even in healthy fish. They may choose to lay on gravel or the broad leaf of a plant. It may also indicate infection or injury though. If hebisbhavibg difficulty reaching the surface, decrease the water level to make it easier. Bettas need to surface occasionally to get some air.

I would recommend to have the water completely changed. New water should be ideally submitted for quality testing. Most pet stores will do this for free or a nominal fee. High ammonia levels, PH imbalances may be responsible for that as well. Oxygen concentration and quality of the filters should be determined 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.