Originally Posted by 1077
Most people recomend water changes of 10 to 20 percent each week with water that has been treated with dechlorinator to remove ammonia, chlorine, and chloramine. Vaccuming one third of the gravel each week a different area each week is helpful in keeping fish poo, decaying plant material, and excess food from fouling the water.(should NOT be done during cycling) filters should be rinsed out in aquarium water that you remove during water changes(NOT Tapwater) shouldn't be done during cycling. Cleaning the decorations is a matter of choice. They can be cleaned with solution of bleach and water at the rate of one tablespoon of bleach per five gal. of water then rinsed well and let dry 24 hours before placing them back in the tank. Hope some of this helps.
All of this applies perfectly to an aquarium set up with old school filtration, such as an undergravel filter or biowheel system. For most of the 1980's, every marine aquarium was maintained using the technique stated above, and it can still be utilized today if you understand the limits of this type system.
For systems set up using a more modern method, with live rock, aragonite or live sand, and a protein skimmer, the concept of "cleaning" is completely different. With such a system, you would not disturb the sand bed under any circumstances. At proper depth and properly established, the sand bed serves to remove Nitrate. This benefit is lost when you stir up the sand with a gravel vac.
Moving on, because the live sand removes Nitrate, water changes for the purpose of Nitrate removal are not necessary. Instead, most of us simply test the alkalinity and calcium levels, and add a simple buffer and calcium solution. This replaces the need for water changes for this purpose, and saves a great deal of cost on marine salt mix.
Such a system is possible because of the protein skimmer. The protein skimmer is the only method of filtration that actually REMOVES organic waste from the aquarium. It does NOT break down organic waste, which results in Nitrate. The skimmer REMOVES organic waste into a collection cup, which is then emptied on a regular basis.
Please note that live rock is necessary to seed the sand bed and process organic waste not removed by the skimmer. Again, in such systems, Nitrate accumulation is zero.
This is why you are getting many different answers. There are a great many people who still use old fashioned freshwater methods of filtration on a marine aquarium. Successful systems can be run this way, but at a great expense long term, both to your pocket book and to the health and longevity of your fish. These systems generally have more "turnover" of fish, with it being rare that a fish lives longer than 3 to 5 years.
Most marine fish in a properly set up aquarium, using live rock, sand, and a protein skimmer, have displayed a life span in excess of 10 years. Many larger fish, such as Puffers, Triggers, and Large Angelfish, have been shown to live in excess of 15 years in captivity. I personally helped a friend set up a 125 gallon tank using such a system in 1991. The first fish was a Clown Tang, Acanthurus lineatus, which still thrives today, 17 years later. This aquarium has never had a water change, other than to remove detritus accumulation from the sump and areas of low water flow around the live rock. Nitrates test zero.
Quick math: doing a 25% weekly water change on a 125 gallon aquarium, at $20 per 50 gallon bag of salt mix... would have cost $8160 for salt mix over the last 17 years. Some people say they can't afford live rock and a protein skimmer. I say you can't afford NOT to use live rock and a protein skimmer.
Personally, I run a 38 gallon reef. I am not as radical as those who choose to never change water, because I believe the fish and corals "respond" better when I do small frequent water changes. Currently, I change 5 gallons every other week. However, there are no detectable Nitrates and I can provide absolutely no logical reason (chemistry) why the water changes are necessary at all.