I have a 120 ltr tank which contains 3 small lionheads and a small fantail.

Yes, I know I am overstocked but I do a 30% water change every week.

However, the water that I am drawing from the tank is coming out when I am cleaning the gravel.

I know you shouldn't clean all of the gravel at once but, I have just read that you should only clean the gravel once a month!

That isn't correct, is it?

I always thought it was the fish poo in the gravel that poisoned the fish.

I need re educating, even after 6 years of running the tank.

Hi
I vac the surface of the gravel once a week, I don't dig it up or root around in it I just go over the surface. Don't know if I'm right but its what i do.

I clean it once a week using the syphon, and give it a good stirring and dig through until the water is running clear.

That is exactly what I do.

I do have quite a wide syphon tube so it does take out quite a bit of water.

Clean ALL gravel.

As those fish need ideally 275 litres as a 'min' before being stunted, you will need to be scrupulous with tank hygiene and water changes. Perhaps even twice or three times a week

Check out the Eheim Sludge Buster - removes poop without removing water in between.

Cheers, off to check out the Eheim Sludge Buster now.

The stuff about not overcleaning gravel relates to under gravel filtration where the gravel held the filtration bacteria. Now most people have internal or external filters so you do want to clean gravel thoroughly, to include stirring it up and digging about in it

I was using under gravel filters in my last tank, I guess I must have just thought the same with the new filter system.

Doh!

I normally clean the tank every monday but ended up doing it at 11pm last night too!

I will start cleaning the gravel every mon and thur from now on, unless needed before that.

I did read that you can't change too much water as the good bacteria is in the gravel, on ormanents, plants etc so it doesn't matter how much water you change.

I thought you shouldn't change a great deal of the water at once, am I right or are they correct about that.

The issue with large water changes is generally to do with pH or Nitrate shock I think.

Adding a large amount of fresh water which has a different pH value can make the fish rather ill, as will suddenly taking a fish in a high nitrate enviroment to a very low one. They need time to adjust gradually to such changes.

Certainly there are times when an emergency water change of up to 50% is required (ammonia spikes, things like that etc) but generally 25% changes weekly with a good gravel hoover at the same time is sufficient for most tanks. Some tanks - both coldwater and tropical - depending on stocking levels and how poopy messy the fish are require twice weekly changes to maintain safe levels

Most fishkeepers aim for zero ammonia and nitrite, and nitrate at less than 40ppm, ideally under 20ppm. I give the gravel a right good dig around each week and that Eheim Sludge Buster I linked to it fab for mid week cleans ups.

The majority of the bacteria is in the filter really, only limited amounts on decor and gravel etc.

Thanks Violet, I saw the Sludge Buster but it is £40 so I will make do with the GravelVAC for time being.