Let's talk about bio load.

[Samw]

Originally Posted by Aquattro

Near impossible for a hobbyist to measure, but that might do it. Perhaps redox values instead?

Why is dissolved oxygen impossible to measure? There are dissolved oxygen meters. I have one.

[Aquattro]

Originally Posted by Samw

Why is dissolved oxygen impossible to measure? There are dissolved oxygen meters. I have one.

Meters are rare items owned by hobbyists. And titration kits don't work well at all.
Not impossible, but not something that is useful, therefore difficult to justify a meter.
Hobbyist meters are also likely not maintained well, so the value could be way off.

[Samw]

Originally Posted by Aquattro

Meters are rare items owned by hobbyists. And titration kits don't work well at all.
Not impossible, but not something that is useful, therefore difficult to justify a meter.
Hobbyist meters are also likely not maintained well, so the value could be way off.

It was useful for me to determine that my tank was overstocked with low DO at night. Without heavy aeration turned on at night, my DO levels were lethal to oxygen demanding fish whereas another reefer who borrowed my meter had a lightly stocked reef where the DO hardly dropped at night. Even with aeration at night my DO was low due to the high bioload.

Here's an affordable one
http://www.amazon.com/Milwaukee-Econ...JCANWD2MRRMSER

[Aquattro]

Originally Posted by Samw

Here's an affordable one

Still $150 bucks! I know so many people that won't splurge on a new refractometer for $40 And that's bit more useful

[Samw]

Originally Posted by Aquattro

Still $150 bucks! I know so many people that won't splurge on a new refractometer for $40 And that's bit more useful

Ok, but if you had one, it can help you determine whether your bioload is too high.

[Aquattro]

Originally Posted by Samw

Ok, but if you had one, it can help you determine whether your bioload is too high.

Ok, I'll give you that

However, that doesn't really address the question.

Skimmer x is good for 200g @ light load, 150g @ med load, 100g high load. How does one determine if skimmer x is appropriate for their 120g tank?

Personally, I've been doing this a couple years now, I just know. I know my bio load, pretty comfortable guessing bio load capacity, and I'm confident in my abilities to size a skimmer.
But for most consumers new to the hobby, what does that mean? Does skimmer x meet my needs? Or do I need x +/-1 for my tank? Generally bigger is better, but if I go too large, I may not have enough load to get proper foam development.

All theoretical discussion with no real answer, just something to kick around.

[Proteus]

Originally Posted by Aquattro

Generally bigger is better, but if I go too large, I may not have enough load to get proper foam development.

Absolutely, found this out buy only running skimmer part time. My skimmer is rate more than double my tank volume and while running 24/7 I only ever got murky water and found it hard to tune the skimmer. Now running at night my skimmate has become very dry and sludgy.
This may put me at a light bioload for skimmer but fully stocked for tank size

[Samw]

I think it does address the question. Your question was how do you know if your tank has light, med, or high bioload: "How do we measure that? I mean, quantitatively, what's a medium bio load? Or heavy? Or medium light? "

So with a DO meter, measure your DO first thing in the morning before there is any light when DO is at its lowest levels. If DO is at 50% or less, you have a high bioload. If DO is 50-75%, you have medium bioload. If DO is 75%+, you have light bioload.

$150 is cheaper than many protein skimmers. Or rent one from a lab: http://www.google.ca/url?sa=t&rct=j&...2hTWDbiE64d4zQ

Originally Posted by Aquattro

Ok, I'll give you that

However, that doesn't really address the question.

Skimmer x is good for 200g @ light load, 150g @ med load, 100g high load. How does one determine if skimmer x is appropriate for their 120g tank?

Personally, I've been doing this a couple years now, I just know. I know my bio load, pretty comfortable guessing bio load capacity, and I'm confident in my abilities to size a skimmer.
But for most consumers new to the hobby, what does that mean? Does skimmer x meet my needs? Or do I need x +/-1 for my tank? Generally bigger is better, but if I go too large, I may not have enough load to get proper foam development.

All theoretical discussion with no real answer, just something to kick around.