It is my pleasure Drmoneejd to both help educate reptile owners with snakes, lizards and turtles primarly with my experiences, education from school and medical experience working 4 years in a exotic vet clinic. Steve the forums highly respected Admin who responded as well has outstanding experience and I do believe that he has way more experience than I do, has always been very helpful working with members. Though I am greatful for your acknowledgements of a thankful demeanor, that alone means so much to me personally and I am sure it is for Steve. To inform you what water conditioning does, it will keep bacteria microorganisms out of your water so it's safe to ingest. It does not dechlorinate the water. In simple terms and understanding dechlorinated water is taking tap water which is considered hard ward, taking the chlorine out of the water making it "soft " , basically safe for fish. What I do and it is strictly my preference for my own turtles with knowing the damage chlorinated water can do it time, I go out of my way and yes pay more for many gallons of all natural spring water and as a precaution I treat the water still with dechlorinated drops for aquariums and water conditioner as well. It gives me piece of mind with my turtles that the water is protected and safe the moment that I put the turtles back into their aquarium and I also use drift wood that is aquarium ready purchased from a pet store. Drift wood naturally dechlorinates aquarium water as well.
Some people think I am a bit crazy spending so much on my pets but I look at it as pets are part of any family. You love them, you care for them regardless of the cost factor. If you can not afford to keep a pet healthy with providing for all their needs, I recommend that those people just do not get a pet that they can't do this for. The water on how I do this, it is only a preference however there is a few ways to obtain soft waters that of course is cheaper and just as good so in no way shape or form do you need to go with how I do it myself. I have the extra money that I put away just for my pets where in today economy, some people can not afford the extra little bit. For those members who may be local to me within a hour drive, I do not mind going out at no cost to them and help address issues with their reptiles. A lunch or some drinks as payments is much appreciated as I would do it for free anyhow just because of my love and respect for the reptiles in general. I enjoyed making house calls under Dr. Sudo's exotic vet orders back in the day giving injections, oral medications, and treatments as well as assisting him at Miami's metro zoo where I obtained yearly passes free for my whole family just for working as his assistant.
Chlorinated water over great lengths of time ongoing has proven bad for aquatic turtles however the good news, is people do not clean their tanks/ ponds / enclosures during the time frame that water can turn soft on its own. Over a twenty four hour period to three days, hard water can turn soft . I hope this explains that part in detail. This of course in not your issue though hard water speeds up a algae problem combined with the bacteria microorganisms.
It is great that you have hotter and colder area of the enclosure and it is good for any reptile. Sunlight and a UVB bulb can and will speed up algae growth of course and I believe you will see a bit more algae around the UVB and warmer areas in your tank but you would need to look close.
Now to your issue that I can see so far is bio balls that you previously had were made for aquariums not only for a wet and dry system but they were also created to maintain a certain level algae and bacteria if you noticed when cleaning and it is needed for certain fish species. So by using the bio balls was indeed part of your previous issue. A long time ago, you could go into a pet store as see that the establishments used these balls for only salt water aquariums for this fact and the corals primarily. Now of days from what I observed they have used the balls for selected predatory fish, brackish water fish, and sometimes but not always certain fresh water fish that I have noticed, take African Cichlids as a example. The reason for the fresh water fish is beyond me however as most but not all fresh water species do not need the algae like other species.
Now the ceramic rings also do a similar function though I have never heard of them creating and promoting algae growth, they do however strongly support and allow waterflow around the turbolates just as it does with a plastic bio-ball for oxygen scavenging. With the waterflow from your 264GPH canister filter around the turbolates in a thirty gallon tank and like Steve questioned about the direct sunlight or I did on the UVB bulb which will promote the rapid growth of algae and expected, will of course speed the growth up tremendously..
Steve may have another possibly thought with his expertise on your question. Other questions I have is what exactly do you have in this tank? Do you have a close up photo of it ? You have mentioned that the dock is home made, What is it made from ?
Below this, I am adding a link of a product on ebay as a example that may be able to control your algae issue with the support of the strong water flow from your 264GPH canister which indeed would be beneficial in rotating the treatment in 18 gallons of water for sure at a quick rate of the ongoing speed per hour. You should see a great reduction of the algae really fast. Though the UVB will promote algae growth going on, I can not see based on the amount of water going through your 264GPH how the UVB would be able to promote the growth in 18 gallons of water or even 30 for that matter, if you use such a product based on directions that the manufacture instructs. Below is the link and I hope it helps you and wishing you the very best as well as a wonderful day.
http://www.ebay.com/itm/like/291719478803