Filter medium

[Shogun]

Hope you dont mind but I have several questions.
How often should rowaphos be changed?
Some people say take bio rings out, others say leave them in. I have had them in till now but have taken them out this evening.
Do I need to have carbon in the filters.
Deltec 600 skimmer has now been running for 7 weeks and is still putting large bubbles into the tank. Is this right? and how often should it be cleaned out thoroughly?

Thanks for any help.

TANK
Juwel vision 180
1000l powerhead
750l powerhead
Fluval 205 external filter with rowaphos (did have bio rings)
Internal filter/pump with some filter floss.
Deltec MCe 600 skimmer
4 x twin tube 16" 36w daylight/blue
2 x twin tube moonlight 16" 36w tubes.
1 computer extractor fan.

Occupants
About 40lb live rock
Thin layer aragonite granules.
5 red legged hermit crabs
1 neon blue hermit crab (freebee)
3 turbo snails
1 skunk shrimp
2 percula clowns
1 fire fish
1 small 6 line wrasse
1 coral beauty
Various soft corals and leathers.
Twist my arm & I'll post a photo.:)

[Germanman]

phosphate resins need to be changed when they seem to no longer do their work. but i remove them every month regardless if they are exhausted or not. as for carbon , its not needed but i recommend it if u plan on having a heavly stocked tank such as mine. also Renew or chemipure are better and less harsh than most common carbons for the reef systems.