I just did my first planting on my 300 gallon tank and I am setting up an autodosing/auto water change system. The difficulty with such a large tank is I can only age and heat 50 gallons at a time so my plan is to do a 50 gallon water change every other day. I'm running ~4 wpg with good c02 injection. The water changes still end up being more than 50%/wk but am I going to accumulate excess nitrates/phosphates etc. doing small w/c throughout the week?

You can take a daily % of dilution and plug it into the equation to see(use infinite series):

See the bottom of this old article:

Practical PMDD Information

Regards,
tom Barr

Thanks Tom
I completely understand the concept but I think my math skills may be lacking.
I'll work on it.

Steve

Take the dose you add daily, and use that.

50/300= 20% if you account for the tank, rocks etc.

So what do dose weekly?
About 25ppm NO3.

25/7= 3 ppm or so NO3.

You can dose daily, you can dose 3x a week, or whatever.
The dilutions will occur about the same as a 50-60% if you do 3x 20% a week I'd say.

Just a quick guess.

Why not use a tub for the water or simply add it back slowly so the warmer water and heater can buffer the temps?

Why do all that for a water change?
I add dechlorinator and use the hot water to mix with the cold.

Solves the issue.

Regards,
Tom Barr

Thanks Tom. It's all making sense now.

Steve

Be careful to really look at the issue before deciding you have to limit yourself and do lots of testing, issues with water changes etc.

The only real work you should be doing: Pruning and keeping up with general care.
If not, then you need to work towards that direction as time and motivation exist.

Regards,
Tom Barr