problem with nitrate > 80

Hello,
I have a all in one tank 400 liter
here is a video of the aqurium

I did a test for water yesterday and i found nitrate to be more than 80
i was having problems with nitrate in another tank (aggressive tank) and it's better now with refuge and DSB
i need advice
should i go for DSB, should i remove every rocks and clean it again
should i go for big water changes
what is the best way to control nitrates
i have no place for sump or refuge for this tank that is why i go with all in ont tank solution
all advice are welcome

 

[FONT=&quot]A large water change will help bring down your nitrates in the short term but keeping excess nutrients out of the aquarium water is one key element in reducing your NO3 in the long run. As you now know, dirty bio media become a nitrate factory, most people don't use any additional bio media besides live rock in their tanks. There are many other things that can add excess nutrients into your tank like some commercial foods which may contain undesirable things like nitrates, phosphates etc and overfeeding the tank is also another factor. Using , RO/DI water, a high quality salt with no NO3, phosphates etc like Tropic Marin or similar good quality salt should really help too.[/FONT]