comments:
Hi; sorry this is happening. Seems that he has some fin rot; this is usually due to poor water quality + incorrect water temperature. (1) Do you have a thermostat? Ideally water temperature should be ~76-80 F. Do you have an API freshwater master test kit? It would be really useful to know the pH; ammonia; nitrite and nitrate concentrations in the tank. I am not familiar with the big als brand; the conditioner removes chloramine, which is the most important step in water conditioning; but it has aloe vera which I am not sure how it aids the fish. It is great that you have a regular water change schedule; and that you are conditioning the water before adding it to the tank. Knowing about the concentration of the nitrogen compounds can tell you whether it's best to do them more frequently or if your schedule works. Do you have an areator in your tank? Proper oxygenation prevents some harmful bacteria growths. Also; (2) do you have any other filter media besides the disposable cartridges with activated carbon? The filter media hosts a large part of the beneficial bacteria that control the nitrogen cycle; and it should not be thrown away ever; instead it is cleaned when it gets clogged with aquarium water. Here's an example of a biofilter sponge I'm also attaching a picture of how my filter looks, it uses that sponge; filter floss and ceramic rings( no need to get the ceramic rings; I recently learned that they are not useful as filtration media for the bacteria). (3)The filter cartridges with activated carbon in planted tanks where you need to add plant fertilizers end up absorbing the fertilizers; thus the plants might not get them. Which plants do you have? Do you have a lighting schedule? Plant health is important in this case because if they start to die and rot; it can cause ammonia spikes and will hurt the fish. Finally; when all of the previous points are addressed (1 being the most important); fin rot can be treated with Kanaplex or fritz maracyn two ( these are not invertebrate safe! You have to remove the snail and the activated carbon before treatment). However; these are antibiotics and can harm the beneficial bacteria in your tank; you would have to be very diligent with the frequent water changes that these treatments require; and some more changes beyond the treatment to keep the toxic ammonia and nitrite at a low beyond treatment while the beneficial bacteria recover. Hope all of this is useful!