Hi there,
dont mind asking more than one, no problem m8.
I never clean the substrate, and I never do resetups ! Thats the worst thing you could do to the aquariumbiotope ! Lots of usefull bacteria house on and in the substrate, and the plants wont appreciate such action, too. Its on old aquaristic myth that is has to be done reguarly, but when done the result is not as good as it was before. I do not recommend undergravel filters, just by the reason that when something is wrong wioth the filter, you have to tear the whole tank apart and have to cycle it again. In most of my tanks I use matt filtration, normally I just cut a piece of filter matt a little buit bigger than the glass of the aquarium side and put the matt into the tank. Then I take a small pump (mostly Eheim compact 300 up tp 1000) stick a piece of PVC tubing on it and put it behind the matt. The pump sucks the "dirty" water through the matt where the usefull bacteria have looots of room to settle and digest Ammonia/Nitrates/Nitrite. In some tanks there is a clued in filterchamber, but in general the filtration there ist the same method just a bit more luxurous ;-)
heres a pic of my Channa sp. redfin tank above water level, you can see various plants growing outside and in the back on the left side, there is the filter chamber. The tube comes out there.
And here you can see my "normal" variant I discribed above, here newly setup.
This filtration runs for years without any maintainance. In one or two tanks I recently took out the matt and squeezed it a bit in a bucket with fresh water, and aftr then I put the matt back in place and the filtration runs on. The usefull bacteria are still in the matt and the Level of Ammonia /Nitrate etc does not increase after such action.
BTW the mentioned two matts were in use for more than three years without doing anything !
I think there are pics from a few breedings online. I have bred (until today) :
-Channa stewartii sp."himalaya"
-Channa sp. "Assam" (often called "blue bleheri")
-Channa orientalis "Kottawa Forrest A" variant
-Channa pulchra
-Channa asiatica
-Channa lucia