Nitrate control

I have a problem with nitrates and its been something ive been battling ever since I started doing fishkeeping where I live. My nitrates tests (by using the freshwater master test kit) between 40 to 80 ppm even after a week, then when I do a water change anywhere from 25% to at the highest (to move a tank) 75% it stays the same. I do weekly water changes and every two weeks I either squeeze out my sponge filters in old aquarium water or clean my canister filters in old aquarium water, and since most of my tanks have 100% silica sand I do hover substrate cleaning every two weeks. The tanks I either have heavier sand or gravel I do gravel vacs every two weeks, Ive tried bio-zorb, bio chem zorb no matter what I do there awlays high. Since I have one female tropheus elongatus is holding right now and soon my duboisi's will be im worried about fry fish growth and the welfare of my fish in general. Also Im on well water with a PH of 8.2 and nitrates out of the tap at 20 ppm.

is it a new tank?

No, they all been setup around 1 to 5 months. 3 of them around 1 to 2 months. Even when they were setup longer with community fish setups Ive always had this problem. Ive changed feeding from twice a day to three times a day with smaller amounts.

hm idk then u may want to ask fern wen she comes on she will be the expert on everything. normally wen u hav that high of a spike its from the tank being cycled but theres maybe more than that then i know of, but i would give all ur info wen fern come on, she would want to know ur reading like ur ph and all.

Have you tried floating plants or a planted sump? quite a few plants will use nitrates as nutrients and help absorb them.

From a little research, I've heard water sprite is supposed to be a good floating plant to soak up nitrates

Water Sprite is excellent for nitrates.

Water sprite works wonders on nitrates. You can probably grow it in a aquaclear filter or some other largeish HOB, it will grow out 1/2 of the water just fine. Or you can make a floating 'plant saver' something that will float in the tank, let the water through and keep the fish out. I can send you a starter bit for cheap if you need it.

Has your test kit been exposed to heat or sun? Sometimes that can mess up the chemicals and throw off your readings. Just for S&G's take a water sample and take it to a lfs for a free test, get all the numbers and see if they are the same as what you are getting.

Oh and stock, tank size and all other readings will help us help you solve this issue.