Water changes are useful for diluting substances which accumulate in the aquarium over time, such as nitrate and other nutrients. They are also useful for replenishing some constituents that are depleted at a relatively low rate, such as magnesium, strontium and trace elements. In aquaria with calcifying organisms such as stony corals, water changes alone are typically insufficient for replenishing calcium and alkalinity.

Frequency and Quantity

My goal is to perform a water change for each of my aquaria every two weeks and each water change is usually approximately 15-20% of the aquarium volume. On average, I change around one third of the water in each aquarium each month.

The Water

I have been using natural seawater exclusively since August 2002. Prior to that I was using either natural seawater or Instant Ocean^® depending on availability. There were periods in 2002 where seawater collection was almost impossible due to consistent bad weather and there was also an extended period when Instant Ocean^® was unavailable. I did not notice a huge difference in the inhabitants when I switched to natural seawater all the time, but I find it is much cheaper and I feel happier knowing that the constituents of the water are much closer to water which comes from a natural reef.

I collect the seawater myself (see: Collecting Seawater) directly into 25 L plastic drums. I either use my water collection pump or I just wade out into the water to fill them. The water pump fills the containers slightly more quickly than with wading, but with the set up time for the pump, total time to collect 600 to 800 litres of water is much the same. I use the 25 L plastic drums for collection, transport and storage. I try to collect monthly. The water may get used on the day it is collected or any time over the following month or more depending on how much I have stored.

Water Preparation

I prefer to heat and aerate the water before use. This is not really necessary, but I feel better having a large volume of aerated and warm water on hand. The water is stored in a SULO 240 L Plastic Wheeled Bin. I have two heaters and two airstones in the bin to keep the water at around 25°C and well aerated.

Water Change Process

The process I follow for each aquarium is basically the same, with slight differences between the aquaria with sumps and those without. While doing the water changes, I take the opportunity to do other maintenance on the aquarium, such as cleaning the glass and the powerhead intakes. For each water change, I remove the determined amount of water and then replace with an equal quantity of fresh seawater.

The tanks upstairs in the house

For the three tanks in the house (6', 180G and 60G), I have set up a pump and piping to get the water directly from the SULO bin to the tanks. This saves me lugging water up the stairs and reduces the amount of time tankef for the water changes. I am able to to do the water changes for all three tanks in under three hours.

The usual process for each tank is as follows:

1. Clean the equipment for the water change which includes: the bin for the removed water (100L for 6' and 180G; 55L for 60G), a 25L bucket, the siphon hose and algae scraper;
2. Place the water change pump (HQB5500) into the SULO bin;
3. Run the extension cord for the pump to the room with the three tanks;
4. Run the 25mm hose from the outlet on the back verandah to the room with the tanks;
5. Turn the circulation pumps off;
6. Clean the front and side glass with my algae scraper. Note I have 2 for the 30" high tanks, a short one for the glass near the surface and a long one for lower in the tank;
7. Turn the auto topoff controller off and raise the float valve out of the water;
8. Turn the sump return pump off and wait for the siphon to stop and the water level in the tank to stabilise;
9. Note the water level in the main tank;
10. Siphon water out of the tank into the bin. The bin lets me know how much I am removing and if I accidently suck up an inhabitant, like a snail, I can retrieve it. I also try to siphon up the algae just scraped of the glass plus any other algae in the tank, such as cyanobacteria;
11. Put the refilling attachment on the end of the hose and place in the tank. The refilling attachment allows water to be pumped into the tank below the water level but immediately breaks the siphon when the pump is switched off;
12. Plug the extension cord for the water change pump into a free socket an turn it on;
13. While the tank is filling, I dispose the removed water down the toilet. I transfer 20L at a time to the bucket which I carry to the toilet.
14. When the water level in the tank reaches the previously noted level, turn the pump off;
15. Turn the sump return pump on;
16. Clean the powerhead intakes, if required;
17. Turn the circulation pumps on;
18. Remove the refilling attachment;
19. Thoroughly rinse all the water change equipment ready for the next tank;
20. Refill the SULO bin;

The tanks in the fish room with sumps

For the two tanks in the fish room with sumps (50G1 and 50G2), I can siphon the new water into the sump.

The usual process for each tank is as follows:

1. Clean the equipment for the water change which includes: a 55L bin for the new water, a 55L bin for the removed water, the siphon hose, the algae scraper and a stick with markings to measure the level of water in the bin;
2. Put 30L of water from the SULO into 55L bin and place the bin on a chair next to the tank.
3. Turn the circulation pumps off;
4. Clean the front and side glass with my algae scraper.
5. Remove macro alage, as required;
6. Turn off the metal halide lamps. This is because many of the corals in the tank are exposed to air during the water change;
7. Siphon water out of the tank into the bin. I also try to siphon up the algae just scraped of the glass plus any other algae in the tank, such as cyanobacteria. I siphon untl the level in the bin matches the line on the stick;
8. Siphon the new water from the bin on the chair into the sump. Note that I do not need to turn the sump return pump off as it is so slow, I can remove the water from the tank before it runs dry;
9. Clean the powerhead intakes, if required;
10. Turn the circulation pumps on;
11. Turn the metal halide lamps back on;
12. Thoroughly rinse all the water change equipment ready for the next tank;
13. Refill the SULO bin;

The tanks in the fish room without sumps

For the four tanks in the fish room without sumps (40G2, 20G, Quarantine2 and Frag), I have to pump the water into the tanks.

The usual process for each tank is as follows:

1. Clean the equipment for the water change which includes: a 55L bin for the new water, a 55L bin for the removed water, the siphon hose, the algae scraper and a stick with markings to measure the level of water in the bin;
2. Put the required volume of new water (30L for frag, 20L for each of 40G2 and Quarantine 2, 10L for 20G) from the SULO into 55L bin and place the bin on a chair next to the tank.
3. Turn the circulation pumps off;
4. Clean the front and side glass with my algae scraper.
5. Remove macro alage, as required;
6. Siphon water out of the tank into the bin. I also try to siphon up the algae just scraped of the glass plus any other algae in the tank, such as cyanobacteria. I siphon untl the level in the bin matches the line on the stick;
7. Attach an Aquaclear 70 pump to the siphon hose, place the pump into the new water and pump the water back into the tank;
8. Clean the powerhead intakes, if required;
9. Turn the circulation pumps on;
10. Thoroughly rinse all the water change equipment ready for the next tank;
11. Refill the SULO bin;

[Home] [Tanks] [Blog] [DIY] [Reference] [The Lab] [About Me] [Site Info]