REASONS FOR WATER CHANGES:

* Nitrate control- A nitrate level of 20 ppm or less is best saltwater, 50 ppm or less for FW (you want a Nitrate level of at least 15 ppm for planted FW aquariums). Please note; an average protein skimmer can NOT keep up with the organic waste output of an average stocked marine aquarium, and water changes for organic removal and nitrate control is still necessary in marine aquarium with a protein skimmer (there of coarse are exceptions in a reef aquarium with large amounts of live rock and live sand, heavy plant or green algae growth, and light animal load- even then added elements need to be replaced in a closed system).

I often have told my customers that Nitrate removal was a ONE (not the only) reason for water changes WITH vacuuming, and it is an important reason. Also as for Nitrates, especially in marine aquariums, removing organic debris before it "cycles" via vacuuming is in my opinion the main focus of nitrate removal via water change.

* Ph and KH/GH control- Maintaining a proper ph (ph levels have a tendency to drop from biological activity), KH is the buffering abilty of the water and that too can decrease. KH is VERY important and a major problem I have seen over the years in my maintenance business when calling on customers who seemed to always have problems with their aquariums and claimed cleaning their aquarium caused their problems, which of coarse is not true. Maintaining a proper GH and KH between cleanings is important. Wonder Shells are one way, arogonite, Calcium polygluconate are others.

For more about this subject, please see this article: How to maintain a Proper KH, why calcium and electrolytes are important.

* Removal of harmful elements. There are many toxins that can be introduced, airborne or in other ways enter the aquarium that are not easily measured.

* Rinsing of bio-sponges, media, ect in used aquarium water (not tap water). This includes sponge filters, bio balls, ceramic media in canister filters (canister filters need to be cleaned more often than many aquarists think)

* Removal of waste before it can go thru the nitrogen cycle

* Control of algae growth

FREQUENCY;

Use these factors to determine frequency:

*Type of fish, such as fish that naturally produce more waste (partly

do to the type of food they eat) such as goldfish where one fish per 8+

gallons is better. Also a large and dirty fish such as an Oscar is another good example.

*Filtration, a properly filtered aquarium (good bio filtration, good mechanical filtration, and good circulation) with multiple filters is important.

*Well maintained water chemistry (including kH and Redox)

*After proper feeding, good cleaning routines (20% water changes with a gravel vacuum once per week or two), proper feeding routines, good filtrations; If after all these are checked off and you still have nitrates that struggle to stay below 40-50 ppm

(20 ppm for saltwater), you probably need to change more water or increase frequency and/or efficiency (especially if there are live plants!). Also a kH and pH that starts out at proper levels, but then drops quickly after water changes and/or addition of stabilizing chemicals or products such as Wonder Shells can indicate poor cleaning routines (as well as other problems such as mulm buildup).

For the full article, please follow this link:

AQUARIUM CLEANING; Reasons and methods for water changes