Water Changes - The Planted Tank Forum
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post #1 of 5 (permalink) Old 05-19-2015, 11:14 AM Thread Starter
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Water Changes

As dosing EI ferts for my 143 litres tank, I have been changing 50% water every week. Now that the plants have reached their optimum capacity, I would like to slow down the process.

If I continue with the same dosage of 30ml but instead of micro followed by macro every other day, can I fert micro and have a day's break and then fert micro and again take a break, and so on also, reduce the pressurized Co2 and reduce the light from 8 hours to 4 hours, can I then change the 50% water every two or three weeks?

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post #2 of 5 (permalink) Old 05-19-2015, 11:28 AM
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water change

Sorry I don't have an answer for you , but that 50% water change every week is a pain in the but. That's why I do pps pro. Check out pps pro at Greenleaf Aquarium. Very little water changes.

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post #3 of 5 (permalink) Old 05-19-2015, 01:32 PM
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The 50% water change ensures that your fertilizer concentrations never exceed double the amount dosed in the period between water changes. You currently dose 30ml every other day, three times a week (or 90ml / week). If you spread this 90ml over two weeks, then the water change would only be needed every two weeks (as an example). You same principle applies to macros and micros.
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post #4 of 5 (permalink) Old 05-19-2015, 01:34 PM
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Focusing on the OP's question:

If you want to slow the growth, reducing light intensity is generally a better idea than cutting back the fertilizers.

Light, CO2 and water produce food energy for the plant. Cutting back any of these will slow growth by reducing the plants energy levels. Taken too far, this results in leggy growth as the plant "reaches" for more light. That said, we can't really cut back water, and cutting back CO2 without reducing light usually results in algae blooms.

Fertilizers are primarily for building cells, reducing these will slow growth too, but generally by reducing cellular health, thus deficiencies occur.

In theory you can throttle growth with fertilizer regulation, but the levels between "slow down" and "unhelathy plant with dying yellow leaves" is pretty narrow. Light level is generally more forgiving.

Now, if your goal is reducing water changes to every-other week, you'd need to cut your total weekly dose in half, at least under the EI model, as imcmaster suggests. However, this isn't really growth-rate related. You can do this at any light level, except maybe "absurdly high"...

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Last edited by mattinmd; 05-19-2015 at 01:38 PM. Reason: more on reducing w/c rate
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post #5 of 5 (permalink) Old 05-19-2015, 01:47 PM
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My water changes are solely for the purpose of removing dissolved organic's for sake of fishes health.(I can take or leave the weed's)
Water changes also provide mineral's that fish/plant's need.
If I wanted to try and reduce the need for weekly water changes ,I would also need to reduce food's and or possibly stock depending on the tank.
Shrimp only tank I have get's water change maybe twice a month.
Fish tank's,50% once or twice a week depending on number's of fish,foods entering the tank, verses plant mass.
I like clean, crisp water, which happen's to suit both the fishes need's and my own.
Spent too much time failing/ learning how to grow plant's without algae to try and run tank's lean or inhibit growth so I tend to stick with what work's best for me in my tank's.
Opinion's vary.

First thing to do if considering reducing CO2/fertz is to reduce lighting IMHO
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