Filter Media Question

[PrairieSunflower]

Right... the story and then the question.
 
For the first time in all my fish keeping... I've had no choice but to replace one of the two sponges in my 10 gallon tank.  When I was giving it a squeeze it actually was coming apart!  Little bits almost like dust (big dust) was coming off.  So.. my filter now has 1 original sponge and 1 new sponge.
 
My tank has been cycled for a long time... over 2 years... not sure on precisely how long.  Up until 2 weeks ago, my tank was pretty much fully stocked for ages.  And then I got a betta... and he died and I got another which is the only fish in the tank now.
 
SO... my question is... will my filter have enough bacteria left to not have an ammonia spike?  If I understand what people have randomly said that bacteria grows to support the amount of ammonia and it dies off a lot slower than it grows.... so... if I have only had 1 betta for the last 2 weeks which is a lot less bioload than I had for ages before that.... now that I only have 1 mature sponge in there... will that be enough to protect my betta from an ammonia spike?

 

[eaglesaquarium]

If you've had a fully stocked tank with 2 sponges and now have only a single betta and one of those sponges, you should be quite fine.   
You lost ~half your bacteria when you replaced the sponge, but your current bioload is far less than 50% of what it had been.  That said, it would still be worth watching for about a week to ensure that it stays fine. 

 

[PrairieSunflower]

Good.  I will test it tomorrow and every 2 days after that if all is well.

 

[bullit]

A couple of water changes for a week for a week will keep on top of anything.