my active carbon in my rena filstar xp4 is starting to deteriorate. i've had it about 1.5yrs. should i replace it??

Yes, by all means replace it! From the sounds of it, it's lasted you a pretty long time!

Activated carbon only lasts a couple of weeks anyway, it's not doing anything that its supposed to be doing in your filter

Yes remove it! Even "high quality" carbon like that used in Rena activated carbon pillows tends to last 4-6 weeks at best so after 1.5 years not only is it saturated, but it most probably has been leaching out some of the pollutants it had absorbed too, which although may not be noticable enough to cause a problem is still not healthy for the fish. On the plus side, it has probably become quite a stable platform for biological filtration too, with colony of beneficial bacteria living on it. When you remove it, I'd monitor your parameters for a cycle "bump" just in case. Whether you choose to replace it again is up to you. Use of carbon in an aquarium tends to be personal preference. I use it in one of my setups with great results, but I change it strictly every 4-6 weeks as it does have a limited useful life

From everything I've read and personal experience, you don't actually need carbon in your filter unless you are trying to remove specific things like medications. I haven't used carbon since I first set up my tanks and haven't noticed any problems.

Yeah, you don't "need" carbon in a filter, unlike mechanical and biological filtration - in most cases chemical filtration media of any kind is an optional element.

However, it can have a place as part of a filtration mix, however it is purely personal as to whether you choose to use it or not.

Carbon is not only used for removing medications as frequently qouted. It can and is useful for (as an adjunct to regular water changes too) for removing other organic pollutants, colourations and odours. It is also acts as a fine filter scrub (like polyester for example) in removing small particles and polishing the water. Over time it can also host beneficial bacteria, although as you should always change carbon frequently, this is less useful and yes there are much better platforms for hosting bacteria (sponges, ceramics etc.)

I think carbon can and does have it's place and I say that as someone who actually uses it regularly and enjoys the very visable results. It all comes down to individual setups and personal preference. Like all chemical filtration media's it is very important to use it correctly in order to get good results and maintain a safe and healthy environment for your fish

thanks guys. i purchased a new net bag and seachem matrixcarbon.

Based on research and information from previous post to your website, I tried since last summer, not use charcoal carbon unless it was an emergency. I recently started back using it again. From my observation, carbon makes lots of difference in the quality, clarity and most definitey smell of the water.

I dont use it. I havent noticed any wierd smells in m water either. I do how ever have a big bag of it if i ever really needed it to remove meds or whatever