So I do water changes in my 200litre tanks every 3 days, Should i be cleaning the gravel this reguarly, they are slightly planted and have corner filters running. Also with the filters I have been told not to clean them but my hang on back filter is getting so gunked up it hardly flows now and this is only after 3 weeks, It has goldfish in it so not sure if this is why, Should i be rinsing it out more often or is it working effectively even though the flow is slow.

HOB filters do block up very quickly, especially with messy fish like goldfish. You will have to keep rinsing the sponges. Just rinse enough, in old tank water, to allow a decent water flow through.

Clean the gravel when it looks mucky. I would not bother every 3 days.

Thank you! Yeah i have been using the tank water to rinse. The bubble/corner filters will need cleaning less often i'm guessing? I have a ramshorn outbreak on one tank and its causing the gravel to get dirty fast hence the regular cleaning, I'm hoping that this is not causing to much disturbance for the good bacteria living in the gravel. thanks again