So I wanted to break down water changes down to how I see them. Basically we have to consider there are 3 reasons to ultimately do a water change.
1) Removing fish waste
2) Resupplying coral with trace elements and everything else in salt mix
3) Nutrients control
So now let’s consider how we approach a water change. If all we are doing is sticking a tube into the water draining water out and simply putting new water in this is going to do #2 and #3 but not remove noticeable fish waste. So why not just really shake up the sand and then suck it all up. This will actually release more nutrients into the water than you would have been taking out, and potentially releasing more fish waste into the water. Don't do it.
Lets assume the main reason we’re doing water changes is because we do not want to dose elements and know by doing a water change we are taking out water with low ppm
and adding in higher ppm
of certain elements water. Removing 380ppm calcium, and adding 500ppm salt mix into the tank can restore levels on a smaller system. I’d have to say a water change of at least 50% would be necessary (with a good amount of hard coral) to get enough ca
, and kh
ultimately. I mean it will do wonders towards keeping ionic balance and providing those minor & trace elements. In a 60g tank a 50% weekly water change is going to cost around $120 a month! DANG! Liquid dosing isn’t even that much and dry powder is even cheaper.
If all you’re keeping is soft corals your levels may not decrease as quickly but surely they will. And if you have a lot of soft corals it could go quicker. Relying on a water change for elements required for corals to grow can put your live stock at risk. If you forget, or get busy these levels will continue to drop. If we get so busy we cannot do water changes the corals life could become at risk.
It is also possible to assume if our only purpose for WC
is elements, if we’re in a rush but want to keep animal going, we may just drain water and not remove fish waste…
Let’s consider water change for the purpose of nutrients being too high. Phosphate is a level aquarist try and keep in trace levels. If you’re at .05 phosphate and want to go down to .03 it’d take almost a 50% water change.. I would also like to ask everyone if we’re okay with keeping nitrate at 10,000 times NSW
why do we worry about phosphate being elevated? There are many examples of aquarist whom have 0.01 phoshate but suffer from hair algae? How can this be so? There’s a few things that dictates algae.. I will not get into it.
If you’re doing water changes to lower nutrients I’d encourage you to step back and wonder why are my nutrients raising and how can I prevent this. Are my circulation pumps moving sand around? Do I have a wrasse who’s digging too much? Have I not removed fish waste in a while?
The single most important thing that a water change [should] achieves is removing built up waste. Detritus and other waste can have serious impacts on corals, including death. High nutrients may effect color pigmentation and growth rates but it will not kill the coral.. there is also a difference between nutrients in the water column and nutrient waste.
It is my opinion that if we are going to do a water change our absolutely main priority needs to be removing the waste from the substrate, filter, and rock. And very slowly as not to release it back into the water column.
Dosing options for ca
are much more efficient, and cost effective than relying on water changes. It is very true for some aquariums a water change makes more sense than dosing because the small amount of corals and coralline algae does not dictate frequent dosing. Cheers, you have designed a low maint coral reef! Keep up the good work.
For the rest of us who have corals who use up calcium like the growing hard skeleton animals they are, we should consider a balanced 2-part system.
The biggest thing for me is ratio. Keeping balance in tact is very important to the reef, in my opinion. If you’re just doing calcium chloride, bicarbonates, and magnesium chloride, you’re completelying leaving out items such as strontium, boron, and many more elements.
A good 2-part or even individual calcium product will contain elements other than calcium in a balanced ratio. Without this balance we will rely on water changes to keep the ratio. (Even nitrogen and phosphate are found in a specific ratio and naturally removed in the same ratio. When we use media like GFO
we disrupt this ratio. Refugium or bio-pellets will preserve the balanced ratio. We can talk about this if anyone is interested. Obviously GFO
is great at what it does, but have we considered the ratio of removal?)
Daily dosed 2-parts will even supply trace elements to the water.
Even with a great 2-part system the salt-mix has everything you need in the ideal ratio and balance. A water change is 99% of the time a good idea for corals…
A lot of aquarist wonder “How often should I be doing a water change and how much water”
Much of this answer relys on which of the 3 reasons you’re doing a water change. If you’re on the Red Sea program testing everything and then resupplying everything then your main purpose of water change is just to remove fish waste. With higher flow most of this fish waste is actually already found in the sump/filter. If you have smaller community fish it is likely you do not need to do water changes often, especially if you skim well and have a larger system.
The smaller the system the more need for water changes always. Levels increase AND DECREASE quicker in smaller volume of water. The smaller the skimmer the more water changes too… To put a number on it is ridiclious but I would say more.
If you’re hardly dosing, and have decent amount of hard corals you should be doing more like weekly water changes if not more frequent.
If you have a grouper and stingray you’re feeding a pack of silversides a day to, may need to do heavier more frequent water changes.
If you have a 55g FOWLR
, you feed 3x a week and only 4 fish (lets say 3 nemo and a dori) you really don’t need to water change often… Especially considering nitrate is not that toxic. But no animal can live in it’s own poo for ever…
Anyway I feel like I have rambled a little and will see if there are any responses to expand this topic on.