waterdrop
Enthusiastic "Re-Beginner"
Sounds like it might be. Good luck. WD
Because it's been 3 months now, my tank is a dirty mess, and I was really confused by that whole processDon't know why you are giving yourself such a hard time! Looks to me like you did a good job.
Water removal and gravel cleaning don't need to be two separate steps: just put a catchbucket at the other end of your gravel siphon hose and capture the dirty tank water you are siphoning out as you deep-clean the gravel. That will be the water (doesn't matter that its dirty!) that you will clean the filter media in. Its easier to just dose conditioner directly to the tank when doing water changes and make the dosing amount 2x what it should be for the tank volume (which of course will be a little less than what they said when you bought it but none of this matters much with small tanks.)
I probably would not have tossed out the carbon layer during fishless cycling but I don't think this is likely to mess you up too much if you still had a pretty good volume of other biomedia in the filter.
OK, another thing, and you can plan to do this next time, no problem that you did less this time, is that "percentage" water changes (like your 5G out of 25G) have no "meaning" during fishless cycling. A kickstart water gravel-clean-water-change during fishless should just be right on down to the substrate taking as much water out as possible. This way you get the maximum re-boost of your calcium, iron, pH, oxygen etc. from the water change. "Percentage" or "Partial" water changes are only necessary for -fish- to lessen some of the potential shock to them and even that is not really needed if you've been water changing on a regular basis so that your tank water params are similar to your tap params.
Now when you clean (gently squeeze sponge, swish ceramic rings, carbon, etc.) the media in the tank water you've successfully protected your bacteria (you keep it wet with tank water the whole time but its not necessary that it be completely submerged the whole time. Short movements through the air will actually give the bacteria a nice dose of oxygen, but just don't let it dry out be inadvertant inattention. The -other- parts, the filter box etc. can be cleaned right under the tap if that's easier, the leftover droplets of tap water will not contain enough chlorine to cause any problem. I just spent the whole morning doing this stuff and let me tell you I cleaned a lot of tank objects under tap water!
If your water change did not achieve a pH of about 8.0 to 8.4 then I'd dose a teaspoon of kitchen baking soda in there to help make it higher. What did the water change get you? Did you remember to plug your heater back in and get your temp back up to 29C/84F?