I am new to this hobby but have kept fresh water tropical fish for a few years. I have a new tank set up and it has been running for almost 6 weeks. So far I just have one red legged hermit crab.
The tank is 120L (around 32 US gallons) and has 20lbs of caribsea 'life' rock (the type that comes dry, but seeded with dormant bacteria that 'wake up' when immersed in water).
I also have one medium marine pure rock (which is a naturally shaped rock). According to their website it is good for filtration of 10 gallons + I have around 2-3 inches of sand.
I have 2 Jebao pumps (maximum 4000 and 8,000 LPH) and hope to have 3 to 5 fish (no coral). I plan on 10-20% weekly water changes, possibly hoping to go to fortnightly in the long term.
My main question at this point is can I get away without any more filtration? I don't have a sump and my aquarium has a fitted, plastic lid. I've already had to bash some holes in the back of the lid to allow for wires and the plastic is really difficult to hack into! For this reason I don't want to add a skimmer or hang on the back filter. I am considering just getting a cheap filter for inside the tank and replacing the sponge with a bag of carbon which I could just use in case of emergency. I know I could just replace the lid, but the advantage to the one I have is that it helps to hide the wires.
Most the the success stories that I have found using this type of filtration are from people who also have a refugium/skimmer/filter sock etc. So, am I asking for problems down the line?
Any advice is much appreciated!