Whar kind of hot water?

[Cazm17]

Just flicking through posts and I saw mention that to bring cold water to temperature you should use boiled water if you don't have a combi boiler?

I have a hot water cylinder and never thought of that being a problem when refilling my tank.

I have 0 nitrites and ammonia, but am constantly struggling with nitrates, could this be a cause?

 

[Essjay]

No, it doesn't affect nitrates.

The reason for not using hot water from a cylinder is because of the cold water header tank in the attic. All sorts of things have been found in header tanks, including dead pigeons. This is why we should not use hot water from a cylinder for drinking or cooking either.

Nitrate gets into a tank in one of two ways.
From tap water. The UK allows up to 50 ppm nitrate in drinking water and many places have tap nitrate almost at this level. It mainly comes from agricultural run off. Test your tap water to see how high yours is.
The other way is being made in the tank. Nitrate is the end point of the nitrogen cycle in fish tanks. If a lot of ammonia is made, a lot of nitrate is produced. The ammonia could come from having too many fish excreting a lot of ammonia; from the fish being over fed, and rotting uneaten food making a lot of ammonia; not cleaning the filter as the goo that builds up in there is fish poop, uneaten food etc which decomposes to make ammonia; not doing enough, or big enough water changes so nitrate build up over time. Do any of these apply?