Help please axie tank weird residue??

so my set up is just under 4ft tank with slate as a base few artificial plants couple of plastic rocks filter with flow reduction...im not sure if the food is related but just incase i have let you know what he was eating...when the axolotl was feeding on blood worm some redy/orange residue was dotting around the tank, i did a complete water change and clean etc and it all went away. he's mosty been eating earth worm lately and instead of spots there seems to be more of a sheet of the rusty looking residue on the slate and plant that in the centre of the tank it doesnt seem to be upsetting the axolotl but wondered if someone could let me know what it is and if i should be worried or need to replace anything its my first axolotl and i was confident with everything untill this popped up

Thank you
Hayley

Some types of worms excrete a fluid which doesn't taste nice, when they feel threatened.

There is no need to be worried. Just wash the worms and keep them in water, maybe shake them a little to make them excrete it, wash them and leave them to soak for a while prior to feeding. That way, your axie will have worms which won't be bothered to excrete icky fluid!

It sounds like brown algae. Harmless, but unsightly. Keeping up with regular water changes and lowering light levels in the tank will help keep it in check.

Thanks loads guys <3