I need a definitive rule on water changes.

[anthonys51]

Nice post! Thanks.



I understand that there is no hard and fast rule, but like anything challenging in life, I try to approach it with some sort of equation and tactic.



Hobbyist 1: "I do a 25% water change every 3-4 weeks"

Hobbyist 2: "I do a 10% water change once a week."

Hobbyist 3: "I do a 40% water change every 6 months..."



My point is...there needs to be some rules for new guys like us.



This is how I would approach it...building off your suggestions



I'm sure if you figure out all the variables (Tank size, Biomass, frequency of feeding, species of fish) you can come up with a rough rule (if you give each species a number ranking based on difficulty).



Lets say that rule ends up being 25% once every two weeks.



Then you can modulate this formula with weekly testing. As long as your test results fall within a given range, you continue with the calculated water change rule.



Any deviation from the testing results should yield some form of modification in wither volume or frequency.



A Nitrate level greater than "x" means that 25% water change every two weeks is now a 15% water change every week until Nitrate levels fall below "x." Then you return to 25% every two weeks.



Sorry...I may seem like I'm sucking all the fun out of this hobby, but for me this is fun. I have an excel spreadsheet for my 16 gallon bio cube, it's the way I approach these sorts of things.

If you want a rule 10 precent a week. Smaller more frequently means less chance of a major change in water parameters when you do do the water chAnge. Test the day before the water change. If your nutrients are still low. You know your doing it in balance. If your nitrates creep up you know you need to increase precent or stop feeding so much . Most likely the later . Now others can do large water changes and be totally ok. It's kind of like saying what's the best diet out there. So many opinions who knows what's really true. But with larger water changes you will run the risk of quickly changing your water chemistry.


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[Stolireef]

You can't do this too often however because you need the bacteria in the water to keep the waste in the water under control. That being said you could probably do a water change every day if you wanted and have super clean water(not recommended).

Sorry, but this comment is absolutely incorrect. The bacteria that live in the water column represent a vanishingly small percentage of the bacterial population that lives on the rock and every other solid surface in your tank. Many experienced reef keepers will perform 50% or more water changes when they sense a problem in their tank. With today's water change systems, many reef keepers perform continuous water changes.

With that in mind, you need to figure out what you are trying to accomplish with your water changes. If nutrient export is your goal, larger water changes are far more effective than smaller water changes. Here's the basic concept.

50% water change will reduce nutrients by 50%

A 25% water change will reduce nutrients by 25%. If you immediately do a second 25% water change, you're only changing 12.5% of the original water for a total nutrient reduction of 37.5%.

If you are going for trace element replacement, then IMO, 10% to 20% change is just fine. The trace elements don't get used up very quickly, especially if you are a FOWLR tank.

No matter your approach, your best indicator of whether you are doing is right is the health of your system. Are you seeing significant algae buildup? Are fish healthy? How about your corals?

 

[anthonys51]

Sorry, but this comment is absolutely incorrect. The bacteria that live in the water column represent a vanishingly small percentage of the bacterial population that lives on the rock and every other solid surface in your tank. Many experienced reef keepers will perform 50% or more water changes when they sense a problem in their tank. With today's water change systems, many reef keepers perform continuous water changes.



With that in mind, you need to figure out what you are trying to accomplish with your water changes. If nutrient export is your goal, larger water changes are far more effective than smaller water changes. Here's the basic concept.



50% water change will reduce nutrients by 50%



A 25% water change will reduce nutrients by 25%. If you immediately do a second 25% water change, you're only changing 12.5% of the original water for a total nutrient reduction of 37.5%.



If you are going for trace element replacement, then IMO, 10% to 20% change is just fine. The trace elements don't get used up very quickly, especially if you are a FOWLR tank.



No matter your approach, your best indicator of whether you are doing is right is the health of your system. Are you seeing significant algae buildup? Are fish healthy? How about your corals?

I agree with this comment except 50 percent water changes don't reduce nutrients by 50 precent. Only reduce nitrates by 50 that are in the wAter. Won't do anything to stuff that hasn't decayed yet. Also you can do 100 precent water change and still won't lower phosphates.


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[Stolireef]

Good point. I should have been more specific

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[JoeyH08]

I have a 90 gallon tank with a 20 gallon sump. I do a 10 gallon change every couple weeks. Ive had my tank running over a year now and have had no problems whatsoever. I post this now and watch something happen. lol.

 

[anthonys51]

Good point. I should have been more specific

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It's ok I'll let it slide this time lol

No
you did a very good job of explaining all joking aside


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[Stolireef]

Even a blind squirrel finds a nut sometimes.

 

[duncanpate1]

OCD + reef tank = disaster!


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[Stolireef]

OCD + reef tank = disaster!


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It depends upon the level of OCD. You know you have a problem if you are testing your salinity every two hours right after you've touched your nose three times.

 

[homer1475]

It depends upon the level of OCD. You know you have a problem if you are testing your salinity every two hours right after you've touched your nose three times.

:lolspin:

 

[Coralfuture]

Sorry, but this comment is absolutely incorrect. The bacteria that live in the water column represent a vanishingly small percentage of the bacterial population that lives on the rock and every other solid surface in your tank. Many experienced reef keepers will perform 50% or more water changes when they sense a problem in their tank. With today's water change systems, many reef keepers perform continuous water changes.

With that in mind, you need to figure out what you are trying to accomplish with your water changes. If nutrient export is your goal, larger water changes are far more effective than smaller water changes. Here's the basic concept.

50% water change will reduce nutrients by 50%

A 25% water change will reduce nutrients by 25%. If you immediately do a second 25% water change, you're only changing 12.5% of the original water for a total nutrient reduction of 37.5%.

If you are going for trace element replacement, then IMO, 10% to 20% change is just fine. The trace elements don't get used up very quickly, especially if you are a FOWLR tank.

No matter your approach, your best indicator of whether you are doing is right is the health of your system. Are you seeing significant algae buildup? Are fish healthy? How about your corals?

I thank you for your elaborations on my comment of diminishing returns. I don't believe this to be ABSOLUTLY incorrect for that I will need scientific proof my friend. Yes, the bacteria is on all the surfaces and few are actually flowing through the water column. However your bacteria's food is in the water and with too little to feed the masses there will be deaths and you may restart the cycle in your tank to some degree or another. Many of those experienced reefers sensing something amiss in their tanks and doing 50% water changes when needed, doesn't sound like a success story for an experienced reefer. Usually when I read or hear about those types of changes its headlined with "My tank is crashing". On a separate note however could you possibly share a link with the continuous water change; that sounds amazing!

Facts are proven in controlled environments

Opinionated facts are what most experienced reefers here share(Myself included)

This is a fun thread lets keep it rolling!

 

[anthonys51]

I thank you for your elaborations on my comment of diminishing returns. I don't believe this to be ABSOLUTLY incorrect for that I will need scientific proof my friend. Yes, the bacteria is on all the surfaces and few are actually flowing through the water column. However your bacteria's food is in the water and with too little to feed the masses there will be deaths and you may restart the cycle in your tank to some degree or another. Many of those experienced reefers sensing something amiss in their tanks and doing 50% water changes when needed, doesn't sound like a success story for an experienced reefer. Usually when I read or hear about those types of changes its headlined with "My tank is crashing". On a separate note however could you possibly share a link with the continuous water change; that sounds amazing!



Facts are proven in controlled environments



Opinionated facts are what most experienced reefers here share(Myself included)



This is a fun thread lets keep it rolling!

Are you disputing the fact that your sand bed or live rock has about a million times more bacteria then your water. It's scientifically proven. Now if you don't want to believe and too lazy to look it up I could really care less.


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[A777flygirl]

Can you advise if you should take water from the sand when doing water changes...or take water from the sump so the sanded is left undisturbed?

 

[Coralfuture]

I see you didn't even read the response. Well this has become like talking to a teenager. Moving on; I personally don't mess with my sand beds at all but I have a lot of snails and a sand sifting goby in both my tanks stirring the sand bed constantly. I take water from the sumps to do my water changes. I avoid messing with the sand bed myself due to the dust storm it would make and that I don't feel it is necessary. If it ain't broke don't fix it. I do however clean my refugium once a year by taking it all out and cleaning it since it's a lower flow area than the tank and I don't have snails or fish to mix it.


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[anthonys51]

I see you didn't even read the response. Well this has become like talking to a teenager. Moving on; I personally don't mess with my sand beds at all but I have a lot of snails and a sand sifting goby in both my tanks stirring the sand bed constantly. I take water from the sumps to do my water changes. I avoid messing with the sand bed myself due to the dust storm it would make and that I don't feel it is necessary. If it ain't broke don't fix it. I do however clean my refugium once a year by taking it all out and cleaning it since it's a lower flow area than the tank and I don't have snails or fish to mix it.


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You will need to clean your sand bed. If it isn't broke don't fix it lol. It's what I told my doctor when he said for me to quit smoking. ( I don't smoke , just trying to make a point)
You want to clean the sand because detritus and stuff accumulates there. Sand shifting gobies don't actually eat detritus. They eat the critters that eat the detritus. Same as sand shifting stars. Pet shops always sell them saying they will shift your sand They will of all the good worms and stuff. But even those worms over time won't keep up with all the detritus accumulating in your sand. That's why you need to clean it regularly if you want to have long term success. especially with sps, might be able to get away with not doing it if you don't stock heavily though . I actually enjoy the fish in a reef tank so I stock and feed heavily


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[Sk8r]

To the op:
This is like watering plants: sometimes the weather has been dry and you need to water more; sometimes when it's rained for a month, you could follow a 'rule' and drown the plant.
The best practice is to test your water weekly for salinity, alk, cal, mg, nitrate. Good readings would be, in order, 1.024, 8.3, 420, 1350, and 5. Take corrective measures if any of these are off.
After that test, change out 10% of your water, ideally from the sump, which makes little disturbance: just shut the pump down, draw water off, put the same amount in, and enter everything including the test numbers in a little logbook, with the date. The reason for the water change is to replace the minerals that aren't alk, cal, mg or nitrate-related. And DO test the salinity of your change water before using.
Do all that and you won't go far wrong.

 

[anthonys51]

To the op:
This is like watering plants: sometimes the weather has been dry and you need to water more; sometimes when it's rained for a month, you could follow a 'rule' and drown the plant.
The best practice is to test your water weekly for salinity, alk, cal, mg, nitrate. Good readings would be, in order, 1.024, 8.3, 420, 1350, and 5. Take corrective measures if any of these are off.
After that test, change out 10% of your water, ideally from the sump, which makes little disturbance: just shut the pump down, draw water off, put the same amount in, and enter everything including the test numbers in a little logbook, with the date. The reason for the water change is to replace the minerals that aren't alk, cal, mg or nitrate-related. And DO test the salinity of your change water before using.
Do all that and you won't go far wrong.

Perfectly said as usual but only thing is I want to disturb the tank. It's a cleaning I blow the rocks clean the gravel. Make it a storm just be careful not to blow the sand all over use one of the python wTer changers and suck a few seconds on the sand the cover with your finger to kill the suction the sand will fall down. Repeat. The food and detritus that comes off the rocks is actually good for the corals and other filter feeders in your tank. I would add the water to your sump if you have one though.


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[thaitopher]

If you dont have a sump I would strongly reccomend 20% a week

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[d0ughb0y]

I am anal and meticulous. I will follow things to the T, which helps in this hobby. The problem is no one has given me a hard rule on water changes.

How much?
How often?

Can someone give me a rule based on:
1) tank size
2) biomass
3) species of fish
4) level measurement results

Etc.
thanks. I need this in terms of math.

this is an art form.

qualitative, yes. quantitative, no.

not everything can be quantified into a formula.

 

[Stolireef]

I thank you for your elaborations on my comment of diminishing returns. I don't believe this to be ABSOLUTLY incorrect for that I will need scientific proof my friend. Yes, the bacteria is on all the surfaces and few are actually flowing through the water column. However your bacteria's food is in the water and with too little to feed the masses there will be deaths and you may restart the cycle in your tank to some degree or another. Many of those experienced reefers sensing something amiss in their tanks and doing 50% water changes when needed, doesn't sound like a success story for an experienced reefer. Usually when I read or hear about those types of changes its headlined with "My tank is crashing". On a separate note however could you possibly share a link with the continuous water change; that sounds amazing!

Facts are proven in controlled environments

Opinionated facts are what most experienced reefers here share(Myself included)

This is a fun thread lets keep it rolling!

First, you don't cycle the water in your tank. The only food the bacteria eat is ammonia and that is constantly being added to the tank by your fish and decaying food. It has been repeatedly shown that the bacteria can actually survive in a completely fallow tank for several monts.

You cycle the bacterial population that lives on the surfaces in your tank. Here's the science. Aerobic bacteria live on the surfaces of everything in your tank. This bacteria converts (technically reduces) ammonia (NH4) to nitrite (NO2) and then to Nitrate (NO3). This population builds up rapidly in a tank and the greater the surface area (eg. the more porous your rock, the more surface area you have and thus, the more stable your cycle).

Deep inside your rocks or under a very deep sandbed, where very little to no oxygen can reach anaerobic bacteria break down Nitrates into nitrogen gas thus providing the final export of nutrients from your tank. This anaerobic bacteria takes much longer to to populate and thus, particularly for young tanks, water changes are a primary method of nutrient export. You really aren't trying to export detritus (which should be handled by your skimmer, CUC, perhaps filter socks, etc. but rather the byproducts of fish waste and the breakdown of excess food in the tank (basically ammonia and phosphates). Basically, water changes (large or small) cannot and do not have deleterious effects on a reef tank so long as they are done correctly (ie. matching temp/salinity and using good quality RO/DI water).

As for links to continuous water changes systems, check out Neptunes DOS, Spectrapure, etc. Pretty much any pair of dosing pumps can be set up to handle this. You just remove a certain amount of water and add the same amount of fresh saltwater.