[Boredomb]

Is the test kit you are using strips or is it a liquid test kit??

 

[Boredomb]

I know with the API master test kit when testing nitrates it important that you shake the #2 reagent like crazy for about 2 mins. I know it says for 30sec but you need to do it more be more actuate. If you weren't doing that that might be some of the funny numbers.

 

[Boredomb]

I would say that is some of the problem if not the root
Overfeeding can lead to this as you may have been aware since you stopped but since the food is still down in the gravel/substrate it will cause nitrates to go up. This is why its important to vacuum the substrate. The next water change you do and everyone after I would vacuum the substrate the best you can going all the way down to the bottom. This will reduce the nitrates as it will get the uneaten/waste from the fish out thus helping the overall water issues.
Having the filter down for a couple of days might have contributed but I think the main cause is not vacuuming/overfeeding.

 

[Boredomb]

Oh you have plants too .... So I know most ppl say don't vacuum the substrate when it planted heavy enough. So in this case I would still vacuum the substrate until you start seeing the nitrates going down and staying down. Then you can just vacuum anything at the surface of the substrate if there is anything there. Figuring out a right potion of food to feed your fish that makes them/you happy but no more then they can eat in 2-5mins and you should be fine.

 

[Boredomb]

20 ppm of nitrates isn't a number I would worry about. Lower is better yes but 20 isn't bad. Its definitely a heck of a lot better then number you had!

Oh I don't exactly live in the middle of nowhere. I have multiple fish stores I can go to in a 45 mile radius. They just don't have the best selection of anything. Most of what I get I have ordered or had the store order.