Cleaning Pipes

Would a bottle brush fit inside the spray bar? If the holes are getting clogged with algae, a toothbrush is useful for that.

I know that some people with externals clean their tubing using a length of string with a weight at one end and a piece of cloth tied to the other end. The weight is dropped through the tube till it appears at the other end, then the string with cloth attached is pulled through.

I keep 2 pipes, when one gets mucky I use the other one and put the mucky one in soak.

I have seen recommendations to use a 3% peroxide in water mixture. I tend to leave mine grubby as they are not visible and the slime is probably consuming Nitrates. I just unblock the spray bar ports with a toothbrush if needed. I leave the filter running and do it before the water change.