Big deep breath @Trakkajack - you don't need to be paying anyone. The Bristlenose issue, is likely the O2 and temp issues we've mentioned already. That Seriously Fish database site that I linked to previously, is my go to for looking up fish requirements - its a fantastic resource as it also often goes into depth on the fish's natural environment, and social behaviour etc. So just make sure you check that site for any fish you may look to add in the future, and/or post a list of potential acquisitions on here, there are some very knowledgeable fish experts on here.
In terms of your filter, there really isn't anything to worry about. I'm assuming you are still using the Oase 600?
To clean the filter, just turn it off (if you have the thermo version, turn the heater off too). Put down a few towels, and have a clean (as in no old cleaning fluid residues in them) empty bucket or two ready. Slide the locking lever across for the pipe inlet/outlet header, and remove it (might take a bit of wiggling to release the seals). This should have locked off the outlet and inlet pipes. If you really want to clean these (I never do), hold a bucket, and lift the filter inlet and outlet out of the tank and directly into a bucket. As you place the bucket on the floor, most of the water should start to run out of them and into the bucket. You can then disassemble and clean all the bits you want to.
Now slide the locking lever on the pre-filter, and remove as normal. Remove the heater if you have the thermo version of the filter, but check it is cool to the touch - if it's still hot, put it back in and wait a while for it to cool before removing fully.
Now undo the four clips and remove the filter head. You can remove and clean the impeller and impellor chamber if you feel so inclined. Again I rarely do.
Now just lift out each basket from inside the canister and clean it. You can do this by rinsing in a bucket of tank water for loose style filter media. For sponges squeeze them out in the bucket of water. Some folks even rinse them under a tap, on the basis it shouldn't significantly affect the bacterial population - personal choice that one. Personally though, I'm a bit lazy, so I just clean them in the water that's already in the canister. I just lift each basket, and give it a good shake in the water before placing them in a dry empty bucket.
Once you've removed all the baskets, pour the mucky water away, and give the canister a good rinse out. Then just put all the baskets back in, put the head unit back on and clamp it down, put the heater and (cleaned) prefilter back in and lock it off. Reassemble all your inlet and outlet pipework, and push the inlet/outlet header back in place and lock it off. Then its just a matter of priming the filter, turning everything back on, and you should be up and running again.
I personally find priming filters a pain - it never seems to work properly for me - so I always fill the the canister (and the pre-filter container) back up with water (to the original level when the baskets were removed) with a couple of drops of Seachem Prime, before adding the filter baskets back in and putting everything back together. You may still have to use the priming pump on the filter if the pipes are empty. If you haven't cleaned the pipes, and they are still full of water though, filling the canister and prefilter with water before re-assembling, should mean the filter starts back up without needing to use the priming pump. It may still need to purge some air, before it gets up to full speed, but it should do that without any intervention.
Ask any questions, and I'm sure either myself or other Oase users can assist (a lot of folks use them on this forum).
