no, not undergravel at all. undergravel filters go underneath the substrate (gravel, sand, whatever). a sponge filter looks like this:
and is not what we have suggested. I don't know if it's commonly used in the UK? quite prevalent across the pond though.
the most common filters you can get here are either a canister (which is external) or an internal. canister filters sit outside of your tank, and you use tubes and pipes to extend the intake and outtake into the tank itself. externals just free up more space in your tank, and also since there isn't really a restriction on size with them, they can hold a lot of filter media (sponges, ceramic rings, bioballs, you name it). the benefits of having this extra media is just because it means more space for more beneficial bacteria to colonise. bb's are part of the nitrogen cycle; one type eat the ammonia produced by the fish and turns it into nitrite, another kind eats the nitrite and turns it into nitrate. live plants eat the nitrate, otherwise getting rid of nitrates is just a matter of doing water changes. if you get an internal filter, it does all the same stuff, just on a smaller scale. it sits inside your tank, but can't have as much media in. it's better to have two filters just because you don't want to be in a situation where, say, it's Saturday night, your only filter fails, nothing's open on Sunday, and you'd have to go without a filter until Monday morning at the very least. it's a good idea to have a back up, even if that means it's only doing half the filtration - at least there's SOME filtration, right??
Eheim is a brand, and they make both internal and external filters. I currently own two internal ones, called Aquaballs. they both do a turnover of 550 litres per hour, so a total of 1100lph in an 160l tank. technically I'm underfiltrated because I have goldfish, but different species of fish call for different needs in filtration - I need 10x the filtration because goldfish are reeeally messy, but if you're going tropical, you won't need 10x. someone else more experienced with tropicals will need to help you with what turnover you need for your 165l! once you know that, you can look on the internet for an internal filter that does half the amount of filtration you need, and simply buy two of them. does that make sense? like, if you end up needing 1000lph, get two filters that do 500lph each or something like that.
I can't help with the heater question since I only run a small tropical tank, so I'm not sure what wattage you need for a tank that big.
I don't know if these are things you've already thought about, but if you haven't, here's a short list of things you either need or might want to have:
- water conditioner, to remove chlorines and chloramines and heavy metals from your tapwater. I recommend Seachem Prime, just because it also does the handy job of neutralising ammonia, turning it into a form that is still edible for the bacteria, but is a lot less harmful to your fish. this is especially good when, like me, your tapwater is treated with chloramines instead of just chorine, because chloramines are created by bonding ammonia and chlorine. so once a water conditioner removes the chlorine, you are still left with a trace of ammonia, which isn't healthy for your fish.
- aquatic plant fertiliser, for obvious reasons haha.
- root tabs, for your plants to absorb nutrients from the substrate. this is optional because the plant fert adds nutrients to the water column, and most plants do well just absorbing those. but you can give them a boost with the root tabs, and they're especially helpful if you forget to dose one week or another for whatever reason.
- a master water drop test kit, so one that you can test the pH, ammonia, nitrite and nitrate levels with, to make sure they're optimal. make sure to get a drop test kit, because strips are notoriously unreliable and inaccurate, especially those "6 in 1" types. I use the API Freshwater Master Test Kit, which has been integral to my fishkeeping, because without it, I wouldn't have known why one of my goldfish lost a few scales (it was because of a pH crash, because sometimes tapwater can come out at something like 7.6, but then once settled in tank, drop to 6.4... this sort of crash is very dangerous to fish health!)
- speaking of pH crashes, I would test the pH, ammonia, and nitrate levels from your tapwater before anything is set up, because some tap water may contain traces of ammonia and/or nitrate, and then leave a bucketful of tapwater to rest for about 24 hours, then test the pH for that. that's just in case your tapwater has the capabilities of dropping after you refill the tank.
I can't think of anything else at the moment, so I hope all that was helpful!
