Do you consider a water change to be an effective type of aquarium filtration method?

[Randy Holmes-Farley]

I have 0 luck with SPS no rapid changes or anything.

I don’t think it is the nitrate in that case. 100 ppm nitrate seems fine for many SPS.

 

[Placenta89]

Biweekly change in my 32biocube. Just to replace elements though. Never had to change water for a long long time due to ammonia or nitrite or anything else. When I eventually upgrade tank size I'll be looking into dosing pumps though to minimize the amount of water changes.

 

[flyfisher2]

With your 20% weekly change you are at about 80% per month. According to @Randy Holmes-Farley 's guide here, I would expect you to almost reach equilibrium after about 60-80 days (about 5 times faster than 15% per month, as you exchange 5 times more per month). So 10ppm after 3 months (90 days) should very close to equilibrium. That gives a monthly net accumulation (without WC) of about 2ppm/week or 8ppm/month.
{equilibrium = accumulation/water change or:
accumulation = equilibrium*water change = 10ppm*20%/week = 2ppm/week}

Using the calculator link provided by @MnFish1 above with your values (150 gallon tank, 30 gallon changed weekly for 3 months = 12 WC and an initial concentration of 50ppm) you can play around a bit with the weekly accumulation to reach your reported 10ppm after 12 WCs. That gives about 1.8ppm accumulation per water change, e.g. 1.8ppm/week.

Thanks for the detailed explanation. Based on nothing more than Nitrate testing on a weekly basis I would say the formula used is very close.
I’m keeping my fingers crossed and hope for a lesser amount of water needing to be changed once I arrive at the level I’d like to see and maintain.

 

[MnFish1]

Thanks for the detailed explanation. Based on nothing more than Nitrate testing on a weekly basis I would say the formula used is very close.
I’m keeping my fingers crossed and hope for a lesser amount of water needing to be changed once I arrive at the level I’d like to see and maintain.

It will all depend on how much nitrate increases each week. In any case, no matter what percentage of water you change you will always level out at a certain level. based on the amount changed - and the rate of production. To maintain that level, you will need to continue the same water change schedule

 

[Sral]

Thanks for the detailed explanation. Based on nothing more than Nitrate testing on a weekly basis I would say the formula used is very close.
I’m keeping my fingers crossed and hope for a lesser amount of water needing to be changed once I arrive at the level I’d like to see and maintain.

I agree with @MnFish1, if you level off at the Nitrate concentration you want, you are exchanging exactly as much water as needed. If you want to stay there you need to continue the same water change volume per time.

Only thing you could change is the frequency of water changes. Exchange double as often, then you only need to replace half as much.
Another thing is that your tank might increase it's own filter capacity over time by building up usefull bacteria/corals that eat the nitrate. You could of course increase this yourself by providing more surface area for those bacteria/corals. Nitrate eating bacteria are, as far as I know from fresh water tanks and I might be wrong, typically anearobic bacteria, so you need to provide them with surfaces in anaerobic spaces. Certain filter media with deep pores do that for example. They also tend to need a long time (on the order of months to a year) to accumulate.
So if your tank increases its own filter capacity you would notice that your nitrate starts to decrease further, even though you are continuing the same water change regimen. Only then you can decrease the amount of water you exchange.

 

[ComfortRacing]

Well simply put IMHO a filtration device pulls water OUT cleans it and puts it back in (skimmers, sumps, canisters etc) the tank stream of flow. Well when you do a water change whether it is weekly, monthly or longer, you are pulling old water out and putting newer water in. So yes it is the human filtration device.

That being said however, my dosers replace what trace elements are used up, my skimmer takes the EWW out, my ATO has a steady flow of pristine water going back in and my reactors are helping (me look real cool) so really i don't need to do water changes unless the proverbial poo has hit the fan.