I need a definitive rule on water changes.

[Stolireef]

I think the whole disturbing the sandbed issue is based on the kind of sandbed. If you have a deep sandbed that is being used for denitrification, disturbing it (especially the deeper sections) can release some pretty nasty toxins (heck if I remember what they are). In shallow sand beds, I think its nice to vacuum up the detritus.

 

[LX20000]

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.

dWater/dt = (sin(TankSize/100) + ln(biomass/100) + SpecieIndex^2) * (NitratesPPM/PhosphatePPB)

 

[Stolireef]

dWater/dt = (sin(TankSize/100) + ln(biomass/100) + SpecieIndex^2) * (NitratesPPM/PhosphatePPB)

Very well said. In other words, the solution to pollution is dilution.

 

[SpottedMoocow]

That's part of why this hobby is so challenging. Some people that run a calcium reactor can go without ever changing water and just topping off as long as their nutrient exports are up to par.

I have plenty of nutrient export methods (biopellets, gfo, chaeto, and use marine pure) and change ~30% every 4-6 weeks. But that's really only to replenish trace elements because I dose Ca, Alk, Mg and acropower.

My suggestion, you'll need to define that WC schedule yourself. If you want a hard fast rule, my rule would be to diligently test your water parameters every 3-4 days and change water as your testing results dictates. Once your tank has settled on livestock and you have a set feeding schedule, you can test less often.

 

[Joe0813]

I do 40 gallons bi weekly on my 180

 

[ca1ore]

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.

As you have realized by now, no hard and fast 'rules'. There's no reliable way to estimate biomass, just the ability to measure the end products of pollution like phosphate and nitrate. My approach has always been to have nutrient export mechanisms that keep those things in check which means 10-20% of total system volume monthly. I go for 'low' rather than 'no'. Keep in mind that water changes also function to replenish depleted elements (though in a somewhat imprecise way); so if you run a calcium reactor, for example, this need may be less.

 

[cscultho]

Slow / Steady / Consistency.

IMO the less you change in your system the better off you will be in the long run. That includes water changes. If you have your system properly stocked with enough bacterial load and a consistent feeding schedule all should go well. yes stuff does and will happen but SLOW and LITTLE change in your eco system will provide the best results.

The oceans don't do water changes....they only get topped off by mother nature.:spin2:

 

[reefteaser]

Cue the cavalcade about how our tanks are not the same as the oceans.

 

[Stolireef]

There's no question that you can maintain a tank successfully without water changes but, IMO, its way more complicated than just doing the changes on a regular schedule.

 

[Johny123]

dWater/dt = (sin(TankSize/100) + ln(biomass/100) + SpecieIndex^2) * (NitratesPPM/PhosphatePPB)

Multiplied by Pi.