Changing filter and cycle

[Karen B.]

Greetings!

I have a 20 gallons community tank, planted, cycled, temp about 75, ph 6.8, kh 2, gh 11, 0/0/10. WC every week or 2 weeks depending.

1 honey gourami, 9 chili rasbora, 7 false julii cory, 5 otocinclus and 4 nerita snails.

There is currently 2 filters : Aqueon HOB quietflow 20 and a sponge filter.

I want to take the HOB with its media and move it to my 10 gallons. I will install a quietflow 30 instead in the 20 gallons.

 

It’s planted, have rocks and substrate, I won’t touch the sponge filter and will keep the presponge filter. Am I ok cycle wise or do I risk a crash?

[Ken]

On 8/29/2021 at 8:14 PM, Karen B. said:

planted, cycled,

If it has been up and running for a few months you'll be okay. If it's recently cycled I'd be nervous. 

[ChemBob]

If it's been set up for a while (several months), I think you'll be fine. Even if it's a bit newer you are probably ok, especially with the sponge filter. You will remove some of the beneficial bacteria. I'd maybe fast the fish for a day before then a few days after you swap out the filters to help reduce the ammonia loss. Best would be if you can run both filters on the tank for a couple of weeks first but I realize that may not be possible. 

[RachelElizabeth]

I did almost the exact same thing you are doing with my 25 gallon. Replaced my old HOB with a new HOB (and brand new media too), but kept the pre-filter sponge and Co-Op sponge filter. If my memory serves me correctly,  I also added SeaChem Stability for a few days to boost new beneficial bacteria populations. It did not seem to affect my cycle much at all. 

That being said,  I had less fish than you at the time (5 cherry barbs and a gourami), so if possible I'd play it safe and try to run both HOBs for a couple weeks.