True that too high ammonia can cause some issues, I would make a 25% water change until you get the ammonia down to about 3-4ppm, I would also lower the temp to 80's area too.
Filter media, if you want to use carbon-go by the package direction on changing but cut the old media off and add to the new media for a week-10 days to seed the new media to prevent a mini-cycle.
If you don't want to use carbon (I don't) you can either make your own filter media or remove the carbon from the store bought media and change it when it is falling apart (1-2 times a year) with just swish/rinse in tank water 1-2 times a month or when the flow slows.
OLF, i have some questions about cycling. I have a 5.5 Gallon tank heated to 90 degrees rightnow. No real plants used. I'm using the cycling with raw shrimp method and my ammonia hit 8.0 yesterday and i removed the shrimp. But today i read that having ammonia that high will actually slow the cycling speed of my tank. Is this true? if so, should i do a water change and how much% ? thank you
I would, but that is me.....I would plant and decorate and add the females, making at least 3-4-50% weekly water changes-this also depends on the number of females you start with and if you have ammonia, nitrite, nitrate test kit-this will make it easier on you. Test daily and make water changes as needed per the test results.
It is better if you do especially in a 10g with sand substrate, do you plan on live plants, if so, that will make thing easier.
You can safely cycle a 10g with a filter with the fish as long as you make the needed water changes of 2-3 50% a week or if the ammonia/nitrite reads 0.25ppm or greater. This is with 1-2 Bettas not overfeed and uneaten food removed