Dosing strategy when smaller water changes are done? - The Planted Tank Forum
 
LinkBack Thread Tools Display Modes
post #1 of 11 (permalink) Old 04-14-2015, 11:57 PM Thread Starter
Planted Tank Obsessed
 
imcmaster's Avatar
 
PTrader: (0/0%)
Join Date: Jan 2015
Location: Newmarket, Ontario, Canada
Posts: 385
Dosing strategy when smaller water changes are done?

With 180g + sump I have over 200g of water. With a sump drain, and a 25g new water reservoir, I change 25g (or about 12%) every 2-3 days. The wc process takes only a few minutes. I prefer this approach to a large change with a python.
The tank has mid-high lighting (including pressurized CO2) so the plants demand quite a bit of nutrients based on the lights.
With standard PPS - I almost also zero out with NO3 and have scale up, plus have gotten GSA and had to increase PO4 to solve that; N:P ratio is about 7:1 right now (not 10:1 as PPS suggests).
I fear over dosing because I have no 'reset' capability, and I feel like I am always under dosing (NO3 is never more than 1-2ppm at the end of a day). I can keep things relatively stable, but I have to measure NO3/PO4 more often, and demand always increases as the plants grow (each week I dose more and more ppm).

You guys have so much experience - maybe there is an approach for a situation like mine. What would you do??

Questions:
- Is my fear of overdosing when water changes are 12% justified?
- Is there a way to make nutrients non-limiting changing only 12% water every 2-3 days?
- If you have chosen to change significantly less than 50% water at a time, can you describe your dosing strategy?

Thank you for taking the time to help. Cheers.
imcmaster is offline  
Sponsored Links
Advertisement
 
post #2 of 11 (permalink) Old 04-15-2015, 12:14 AM
Planted Tank Obsessed
 
PTrader: (0/0%)
Join Date: Jan 2014
Location: Denver, CO
Posts: 400
might get a TDS/EC gauge and check overall PPM before the WC and attempt to dose back to the same level it was at once everything has settled. Is your new water 0ppm?

something tells me though eventually your going to need to do a major water change just to discard unused minerals... taking a little bit at a time and replacing the solution is not going to be as stable as larger water changes, and since there less frequent that promotes stability more.. your strategy seems to be a constant battle of trying to figure out whats been consumed and what hasn't been and replacing that without concentrating the nutrients, ugh.

Can you stash a recycled 55g drum or two to store more new water in so its easier to do a bigger water change? You have a giant tank, with less frequent but larger PWC's it should be very stable and predictable parameters.


To view links or images in signatures your post count must be 10 or greater. You currently have 0 posts.

5 Gal Tropic Nano w/SunSun 603b,
To view links or images in signatures your post count must be 10 or greater. You currently have 0 posts.
nayr is offline  
post #3 of 11 (permalink) Old 04-15-2015, 12:43 AM Thread Starter
Planted Tank Obsessed
 
imcmaster's Avatar
 
PTrader: (0/0%)
Join Date: Jan 2015
Location: Newmarket, Ontario, Canada
Posts: 385
I could use straight tap water - but the gH is higher than I like (around 15); kH is OK - I just never felt comfortable adding 100g of tap water (adjusted to 78 degrees) to the tank. Perhaps I am over-thinking that.
I don't really trust Prime (or Safe) for 100g of tap water; it will deal with the chloramines, but will create a lot of ammonia in the process. Prime will bind it up for only about 24 hours. Am I correct in this? And I prefer to use cold tap water (and age it 1-2 days to room temp); I have had a few hot water tanks that appear to stain the water over time.

So for a few minor reasons, I would like to keep exploring a sustainable tank changing only 25g at a time. But I agree with what you are saying, and perhaps I'll have to do a large change every couple of months? Just don't want to do one every week....

PS: My fish room doesn't have space for much more than the 25g holding tank now.

Last edited by imcmaster; 04-15-2015 at 12:45 AM. Reason: No space for 55g or two...
imcmaster is offline  
 
post #4 of 11 (permalink) Old 04-15-2015, 02:22 AM
Planted Tank Obsessed
 
PTrader: (0/0%)
Join Date: Feb 2010
Location: Woodstock, IL
Posts: 354
If you change one half the water, fertilizer levels will stabilize after several weeks at 2 times the amount of ferts you add. If you change one third the water, fert levels will stabilize at 3 times the amount added. one quarter water change = 4 times amount added.

1/8th water change (12%) means ferts in the water column stabilize at 8 times the ferts added each week.

So if you want to do 12% water changes, you'd need to dose at 1/4 the normal EI dosing levels to stabilize at the same levels as EI with a 50% water change.. Keep in mind it will take several weeks to build up before stabilization occurs so you could probably start with a higher first dose to get the concentration up faster.
dmagerl is offline  
post #5 of 11 (permalink) Old 04-15-2015, 02:52 AM Thread Starter
Planted Tank Obsessed
 
imcmaster's Avatar
 
PTrader: (0/0%)
Join Date: Jan 2015
Location: Newmarket, Ontario, Canada
Posts: 385
Interesting and good to know - thanks. I feel like this model can work.

Taking KNO3 (or K) as an example, the IE calculator says to dose 7.5ppm 2-4x per week. One quarter would be about 2ppm dosed 2-4x per week.
Interestingly, I already dose more than this, and NO3 never climbs (i.e. my plant demand must exceed 1/4 EI dosing).

So I must have to do what you suggest - 'superdose' once to crank up the levels, then ease off to 1/4 dosing afterwards?
imcmaster is offline  
post #6 of 11 (permalink) Old 04-15-2015, 05:14 AM
Planted Tank Guru
 
PTrader: (0/0%)
Join Date: Jan 2010
Location: Contra Costa CA
Posts: 11,721
Step 1: Have you calibrated your NO3 test?
https://www.plantedtank.net/forums/sh...ad.php?t=83545

I would not over dose, but increase your dosing just a bit, then monitor it for a week or two, (3-4 water changes) and see if it is trending upwards, and where it starts to level off. Perhaps increase your dosing by 25% (dose one more time per week, or a little more each time you do dose)

I have done something close to 100% water changes on some tanks (oops- sorry fish, they were almost stranded) and refilled with tap water. My tap water shows 1 ppm chlorine and 1 ppm ammonia from chloramine. Prime and similar products (I have used Chloramine Buster a lot) work just fine as a dechlor.
Think of it this way:
Before you did the water change the water had some ammonia from the fish and from decomposing things in there. The bacteria is used to dealing with that, and can handle that much ammonia spread out over the course of the day so you cannot tell there is any ammonia present.
When you do a water change you are removing whatever ammonia is in the water and replacing it with ammonia from the tap water. So the bacteria get to work on this. The Prime keeps it from being toxic, and before the Prime is deactivated the bacteria have handled all the ammonia.
The plants also take in ammonia- most aquatic plants prefer ammonia over nitrate or nitrite as their source of nitrogen.

If you do 2 water changes back to back with that small a storage source it is not a whole lot better. However, if this method is working for you, keep on going with it. Use those small water changes to vacuum the tank almost every time, and clean the filter media as needed. But really look into a larger prep method. Some disaster could happen that can best be solved with a much larger water change, and being able to have more water ready to use can make the difference. Perhaps think about prepping RO in the barrel (no GH booster) and matching it with tap water (which supplies excess GH) with the net result that you could possibly do a 50% water change in case of emergency.
Diana is offline  
post #7 of 11 (permalink) Old 04-15-2015, 02:11 PM
Planted Tank Obsessed
 
PTrader: (0/0%)
Join Date: Feb 2010
Location: Woodstock, IL
Posts: 354
Quote:
Originally Posted by dmagerl View Post
If you change one half the water, fertilizer levels will stabilize after several weeks at 2 times the amount of ferts you add. If you change one third the water, fert levels will stabilize at 3 times the amount added. one quarter water change = 4 times amount added.
I should clarify this statement. The statement disregards any subtraction due to plant uptake of the nutrients.

If plants are removing a significant portion of the nutrients, then you will not see the stabilization at 8 times ferts with a 12% water change. It will stabilize at some lower amount. In fact if you go with the 12% water change, it may be entirely possible that one quarter of the regular EI dose may be too little to sustain your plants. You could end up under dosing your plants.

Doing a 12% water change means you have a cap of UP TO 8 times the dose rate, it doesnt mean you WILL have it. It could be much less depending on plant uptake of the nutrients.

The whole purpose of EI is that you provide a non limiting supply of nutrients without having to do any kind of extensive monitoring. Doing a 12% water change leaves you having to worry if a 1/4 dose is enough. It certainly means you should be monitoring things more closely, which isnt what EI is meant for.
dmagerl is offline  
post #8 of 11 (permalink) Old 04-15-2015, 02:50 PM Thread Starter
Planted Tank Obsessed
 
imcmaster's Avatar
 
PTrader: (0/0%)
Join Date: Jan 2015
Location: Newmarket, Ontario, Canada
Posts: 385
Thanks all. It is confirmed that I need to tune the dosing and stay on top of measurements if I keep with the smaller water changes. This is not a problem. It is a bit useful to know the plant uptake.

I haven't calibrated NO3 (or PO4) - but have the test kit where you measure out the powder prior to shaking - and have seen various colours from yellow to slight brown (just never anything approaching red) for NO3 (and various blues for PO4), so I believe the measurements to be good.

I'll prepare for a 50% wc as well in case of emergency. Thanks again.
imcmaster is offline  
post #9 of 11 (permalink) Old 04-16-2015, 01:40 AM
Algae Grower
 
PTrader: (0/0%)
Join Date: Mar 2014
Location: Va
Posts: 119
I really think you are over thinking, but being prepared for any eventuallity is smart
GoodOldDays is offline  
post #10 of 11 (permalink) Old 04-16-2015, 02:37 AM
Planted Tank Guru
 
Zorfox's Avatar
 
PTrader: (5/100%)
Join Date: Jun 2012
Location: Gainesville, FL
Posts: 2,105
I didn't see what you're actually dosing. Did I miss it?

If you change 12% every 2-3 days then you're easily doing 24% per week. Non-limiting nutrients is totally doable at that ratio.

I'm not sure if you've seen this part of YANC (yet another nutrient calculator). It models what your nutrient levels will be based on water changes, dosing and plant uptake.

Use straight EI entries for all the questions (7.5ppm dose, 50% weekly water change). You'll see the nitrate range levels off at 45-37.5 ppm. Try and duplicate those ranges using your water change schedule. In your case, about 4ppm and 24% weekly water changes seem correct.

Naturally, you duplicate that for each fertilizer. Then you have a good starting point. You may need to increase or decrease but it's in the ball park.
Zorfox is offline  
post #11 of 11 (permalink) Old 04-16-2015, 03:00 AM Thread Starter
Planted Tank Obsessed
 
imcmaster's Avatar
 
PTrader: (0/0%)
Join Date: Jan 2015
Location: Newmarket, Ontario, Canada
Posts: 385
Nice!
I am currently dosing about 1.3-1.5ppm of N and K, and about .16ppm PO4 per day, and still no appreciable rise in either NO3 or PO4 (fast growing plants must soak them up) ... plus micros. Now I can push this knowing things will stabilize according to that calculator.

I'm finally looking forward to a non-limiting approach. Thanks Zorfox.
imcmaster is offline  
Reply

Tags
None

Quick Reply
Message:
Options

Register Now



In order to be able to post messages on the The Planted Tank Forum forums, you must first register.
Please enter your desired user name, your email address and other required details in the form below.

User Name:
Password
Please enter a password for your user account. Note that passwords are case-sensitive.

Password:


Confirm Password:
Email Address
Please enter a valid email address for yourself.

Email Address:
OR

Log-in










Thread Tools
Show Printable Version Show Printable Version
Email this Page Email this Page
Display Modes
Linear Mode Linear Mode



Posting Rules  
You may post new threads
You may post replies
You may not post attachments
You may not edit your posts

BB code is On
Smilies are On
[IMG] code is On
HTML code is Off
Trackbacks are On
Pingbacks are On
Refbacks are On

 
For the best viewing experience please update your browser to Google Chrome