Welcome to the forum and sorry your Betta isn't well....
It sounds like poor water quality and too cool of temp has caught up with him and compromised his immune response.....but this is an easy fix in most cases.....
In the 1.5gal filtered tank-I would recommend twice weekly water changes of 50%...1-50% water only and 1-50% to include the substrate by vacuum or stir and dip method
Filter media needs a swish/rinse in the bucket of old tank water with a water change a couple of times a month....
Filters are optional for this species and sometimes in the smaller tanks the water movement can stress them.
Filters can help to remove the larger debris from the water column-but until the biological filter is established the debris is being recycled over and over in the filter and water changes are still needed on a regular bases to keep ammonia controlled as well as the DOC's
If you remove the filter-water changes of twice weekly will still be needed...1-50% and 1-100% to maintain water quality....
Nutrition is also really important-a good quality varied diet fed in small frequent meals-don't overfed and remove any uneaten food within a reasonable time.....
You may need to get a heater-it is important to maintain a somewhat stable temp in the 76-80F range
You do need a thermometer to monitor both the tank temp and the temp of the replacement water used for water changes-It is important to try and keep the water temp between the new and old water within a few degrees of each other to prevent temp shock-extreme sudden temp changes can be stressful and sometimes kill Bettas.....
Right now-I would get a heater to get the temp up and do 50% daily water changes for 2-3 days and see if this will perk him up and then get on a regular water change schedule to maintain water quality and prevent health and fin issue...
Keep us posted...if he doesn't perk up in a few days with increase temp and water changes-he may need a treatment....
Also, can you post a pic....
It sounds like poor water quality and too cool of temp has caught up with him and compromised his immune response.....but this is an easy fix in most cases.....
In the 1.5gal filtered tank-I would recommend twice weekly water changes of 50%...1-50% water only and 1-50% to include the substrate by vacuum or stir and dip method
Filter media needs a swish/rinse in the bucket of old tank water with a water change a couple of times a month....
Filters are optional for this species and sometimes in the smaller tanks the water movement can stress them.
Filters can help to remove the larger debris from the water column-but until the biological filter is established the debris is being recycled over and over in the filter and water changes are still needed on a regular bases to keep ammonia controlled as well as the DOC's
If you remove the filter-water changes of twice weekly will still be needed...1-50% and 1-100% to maintain water quality....
Nutrition is also really important-a good quality varied diet fed in small frequent meals-don't overfed and remove any uneaten food within a reasonable time.....
You may need to get a heater-it is important to maintain a somewhat stable temp in the 76-80F range
You do need a thermometer to monitor both the tank temp and the temp of the replacement water used for water changes-It is important to try and keep the water temp between the new and old water within a few degrees of each other to prevent temp shock-extreme sudden temp changes can be stressful and sometimes kill Bettas.....
Right now-I would get a heater to get the temp up and do 50% daily water changes for 2-3 days and see if this will perk him up and then get on a regular water change schedule to maintain water quality and prevent health and fin issue...
Keep us posted...if he doesn't perk up in a few days with increase temp and water changes-he may need a treatment....
Also, can you post a pic....
