Need help with a betta

[Wiggy]

Do not use distilled water for water changes in your aquarium, unless you are mixing it with tap water for the purpose of dilluting minerals to soften the water and bring down the pH.

The minerals introduced through your tap water are essential, and doing water changes with pure distilled water will cause fluctuations to your PH, GH and KH.

The beneficial bacteria in a bottle products marketed are of questionable value. There are several logistical issues with the feasibility of a product like this (ie. how do you keep aerobic bacteria alive in an air-tight container without a food source?). Regardless of whether you think these products are worth anything or not, if your regular maintenance is dependent on them, then you have a fundamental problem.

Beneficial bacteria is not present in the water column. It covers the surfaces of the aquarium, substrate, decor, etc. So if anything, the fact that you're scrubbing everything down is what's removing it, not the fact that you're changing the water. Large water changes are ill-advised because of the sudden swing in water chemistry they cause, which the fish hasn't had time to acclimate to properly, not so much their effects on the bacteria.

If your city treats its water using chloramine you must use a water conditioner to remove this. If your water is treated with only chlorine, it is fine to leave it out to dechlorinate on its own, but be aware that the oxygen content will be low.

Personally I would use water conditioner regardless to save time. Use Seachem Prime. It's a very concentrated formula, and over the lifespan of a bottle, is actually the cheapest brand I've found. It also has the nice benefit of ionizing ammonia into ammonium, which is non-toxic, but again, should not be relied on. It's more of a nice thing to have in a pinch.

Get a filter. Another route to address the problem would be live plants, but I would say look into that later and for now just cycle a filter and use it. Chemical filtration (carbon) is optional, but I've never bothered using it and find that having to replace it frequently is just another hassle and expense. A simple sponge filter should be adequate. Bio-media would be nice too, but you have a very low bio-load so you really don't need much of a filter. Just something.

I highly recommend a heater. Bettas are tropical fish, and thrive best in tropical temperatures.

I would also recommend a larger tank. Ideally I would recommend 5gal or larger (provided adequate cover. I kept my last betta in a 29gal planted community). Waste concentration will accumulate slower in a larger volume of water. Water parameters are more stable, and bettas do actually appreciate a little room to explore and swim. They can be fairly active and curious when housed in ideal conditions.

In regards to the almond leaves....

I use them. They're great. But would not address the problems this fish seems to be having.

EDIT: I should also mention that around this time of the year it's not unheard of for ammonia levels in our tap water to rise, due to the thawing snow. Water companies also put more additives in the water. Just another good reason to use conditioner regardless.