I am doing a 10% water change weekly

In my bin I use a flavel 4 pump with sunge filter and heater, they are getting slime growing on them after a month or so, is this harmful ?

Just an other thing to clean.

try the beach

Yip...the beach!

The slime will not be harmful.

What it does show though, is that somehow there are nutrients in your water, enough to make the slime grow.

However, the slime is in fact using these nutrients, so when you put the water in your tank, leave the slime behind, it will have absorbed some unwanted nutrients.

do you have and are you using RO or DI or both?

I use tank water.... in the country

tested it? just incase?

Duke I'm not totally sure where you are, however the water out of a country tank can contain, among other things, bird crap off the roof, fertilisers, and spray drift.

You should test the water for phosphate, and also it would pay to at least run it through a carbon filter prior to use.

Don't think that just because you drink it, it must be fine for the tank. Our bodies are capable of dealing with much more polluted water than we can put in our tank.

Not trying to scare you, but whatever is in the water may slowly accumulate in the tank and cause problems in time. Just be aware and take the right precautions and you'll be fine.