Betta died of fungal infection, when can I add a new betta?

Question

My little betta passed away after a long struggle of being sick, getting better, being sick. He finally developed a fungal infection that I couldn't kick and he passed away. In the immediate moments of despair that followed, I emptied the tank, vowing to never own fish again because that little dude stressed me out, but now I want another one because fish are just wonderful little pets.

I'm not 100% what type of fungal infection he died of, he had cottony growths appear suddenly on his final day alive, but I'm wondering how long I should cycle the tank before reintroducing another fish. Here are my questions, in no particular order:

1. How much I should scrub things that were in the tank?
2. Should I replace the black sand substrate, or should I leave some of the natural bacteria from the tank?
3. I have 2 moss balls, 1 zebra plant, and 1 madagascar lace plant - would they have a possibility of retaining fungus? How do you clean live plants?
4. I already threw the existing filters away, and my filter motor has some algae growth in the tubing that I can't clean out - should that concern me, or is some algae okay?
5. Should I upgrade to a 10 gallon? This last tank had ridiculous algae growth that I couldn't control, something I did not experience with the first betta I owned. I tried a snail, but my betta killed it, so I'm hesitant to try that again. I think a 10 gallon could help this?

Answer 1

You need to vacuum the gravel and do your normal maintenance of your tank

(clean your filter-remove dead parts of plants-do a water change).

A fungal infection in your fish is normally the result of elevated levels of ammonia and/or nitrite in the water. This will weaken your fish so that their immune system is unable to fight the fungi or bacteria that is a normal part of the biology in a tank.

Removing the filter media will have removed some of the good bacteria you need to have in your tank. This means you will have to cycle your tank again (this does not have to take a lot of time, lots of bacteria is living in the gravel and on the surfaces in your tank). Please take a look here on how to cycle a tank https://www.fishlore.com/NitrogenCycle.htm

In a larger tank the water parameters will be more stable, so the larger the tank the less the water quality will change over time.

Having some algae on your pump or rocks is not a problem, and you do not need to change the gravel, you only need to clean it.

In a fish tank, focus on the water quality, because if this is good your fish will live a good life until they die from old age :)

Also, read about the needs of the fish you want to get,The staff in petshops in general have no idea on how to keep the fish alive only how to sell them.

You can add new fish only AFTER your tank is properly cycled (please see the link I have provided).