Join Date: Jun 2010
Location: Northern Virginia
Unfortunately, it is not possible for algae to kill an animal like a betta or a snail. Rising ammonia levels in the tank due to the waste output from your betta or snail can cause algae to bloom. Algae is a side-effect of the problem, but it is certainly not the problem.
What you have to understand is that fish constantly release a toxic substance called ammonia through their gills as they breathe. This is sort of like the fish's version of urination. Ammonia is a very unpleasant substance--it's the source of the foul odor in window cleaners and all-purpose cleaners that they try to cover up with perfumes. In weak concentrations, it will slowly wear down your fish's organs and their ability to fight off diseases, ultimately leading to sickness and death. In high concentrations, it will literally burn away the fins and the gill tissue. Not a pretty way to die.
In nature, this ammonia is consumed by beneficial bacteria, that convert it into a less harmful substance, it is also consumed by plants, and diluted over much larger quantities of water. Since none of these components are at work in small, unfiltered, uncycled betta tanks, you must compensate for this with very frequent 100% water changes. For instance, a 1 gallon container will need a 100% change every other day, a 2 gallon container will need a 100% change every 3 days, and a 5 gallon container will need a 100% change once a week.
The reason why you need to do 100% changes is because if you change 50% one day and 50% the very next day, technically this adds up to 100, but you have not changed 100% of the water. Inevitably there is some of the old, fouled water left, plus whatever your fish added to it in between, so over time these partial changes become less and less effective at controlling ammonia.
Your problem is that the ammonia levels in your tank are too high and the tank is receiving too much light. If the tank is getting any direct sunlight during the day, move it. It is not healthy for your betta and that is the fastest way to get waaay too much algae. If the tank has its own light, try to keep it on for only about 6 hours a day.
Even if you get a snail or whatever, if you don't eliminate the source of the algae it will continue to be a problem. Personally, I would skip the snail. Snails just turn algae into poop, which is just as unsightly and it contributes to the ammonia level in your tank.
Emergency? Need immediate advice? Create a thread on bettafish.com about your topic of concern and then check out #bettas on irc.shadowfire.org to chat live with other betta enthusiasts -- click the link below to learn how.