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I have a 72g bowfront, medium planted, running pressure C02, two 54w T5 lights at 9 hours a day. Has been setup for 4 weeks and I just installed the C02 yesterday. KH was 8 and my ph was 7.8.

I'm just starting dosing and am using the following I found on the internet as a starting point..

60 – 80 Gallon Aquariums
+/- 3/4 tsp KN03 3x a week
+/- ¼ tsp KH2P04 3x a week
+/- ¼ tsp (20ml) Trace Elements 3x a week
50% weekly water change

Easy enough so it seems for this old retired NASA engineer.. I wanted to make a solution for 4 weeks so I did this..


KN03 Target 20ppm Per Week

3/4 tsp 3x week = 2 1/4 tsp week x 4 weeks = 9 tsp = 3 Tablespoons = 12 doses

Mixed in 180ml distilled water Chucks Calculator shows .4ppm per 1 ml x15ml dose = 6ppm dose x 3 = 18ppm a week... Great..

Plantex CSM

1/4 tsp 3x week

2 Tablespoons in 500 ml and dose at 10ml 3x week

The problem..

KH2P04 Target 1ppm per week

1/4 tsp 3x week = 3/4 tsp a week x 4 weeks = 3 tsp = 1 Tablespoon = 12 doses

Mixed in 180ml distilled water Chucks Calculator shows .2ppm per 1 ml x15ml dose = 3ppm dose x 3 = 9ppm a week

Note: This just doesn't work out with Chucks calculator.. but all the sites recommend 1/4 tsp three times a week. Sure looks like that is way over the recommended dose or I'm missing something.


Could I get a little help here, I sure would appreciate it. I really have the goal of a great planted aquarium to enjoy and work with in my retirement years.
 

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I think thios might because theese are dosing standards for EI? So u does extra ferts and then do a water change weekly to balance out any ferts of access to any that are low. I could be way off here but saw no one had responded yet gl
 

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You will need to suspend that light about a foot above the top of the tank to avoid a constant battle with algae. Another advantage of doing that is that the light intensity will be much more uniform in the tank. Your fertilizing looks about right.

Incidentally, I used to be a NASA engineer too!
 

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Sure looks like that is way over the recommended dose or I'm missing something.
The missing puzzle piece is that the extra phosphate isn't really for the plants at all.

1-2ppm is enough for plants, but higher levels of phosphate suppress green spot algae (GSA). You can have a perfect tank setup, and healthy well-fertilized plants, and GSA will still appear unless phosphate levels are kept up beyond what plants need.

The exact amount of extra phosphate recommended for this varies, and isn't particularly critical. For example, on this forum there's a guide with different recommendations:

60~80gal
3/4 Tsp-KN03 3x a week
3/16 Tsp-KH2P04 3x a week

A bit less than what you posted, at 4:1 ratio by dry measurement. I've experimented and found I can reduce phosphate dosage as low as 6:1 without GSA, though there's usually no practical reason for doing so.

But if I aim strictly for the recommended tank concentrations of 10-20ppm nitrate and 1-2ppm phosphate, I get GSA all over the place. :)
 
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