Is it normal to have to dumo phosphate in your tank? - The Planted Tank Forum
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post #1 of 6 (permalink) Old 03-31-2019, 09:56 PM Thread Starter
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Is it normal to have to dumo phosphate in your tank?

20 gallon long tank. Aiming for 20ppm nitrate and 5ppm phosphate.

I need to put in about 1/4 tsp of mono potassium phosphate into my tank 4-5 days a week to keep it at 5ppm. It drops like crazy overnight. It's almost always at 1ppm~ the next morning. This has caused two multi-week long algae blooms for me in the past. Each time I turn up my light, my phosphate intake increase at what seems like an exponential rate. So yeah, I've been finding out what the tank needs after light intensity increases the hard way. Hint: it's phosphate.

I have no issue keeping my nitrates around 20-40ppm just from what I assume is the fish bioload alone. I have to dose potassium nitrate MAYBE once a week at best. Some weeks I have to do extra water changes just to get it down. Because of this, I dose a decent amount of potassium sulfate as well.

Is this normal? I always hear people who don't know what they're doing saying dosing phosphate causes algae. I can definitely say that the LACK of phosphate with a high-ish nitrate is what causes algae, all other parameters being at the correct level.
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Last edited by Ddrizzle; 03-31-2019 at 10:31 PM. Reason: edit
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post #2 of 6 (permalink) Old 03-31-2019, 10:58 PM
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I'm curious to see some answers, as I am currently dealing with almost the same thing, minus the algae. I just can't seem to maintain any PO4 in my tank, while NO3 climbs to 40-80ppm by the end of the week.
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post #3 of 6 (permalink) Old 04-01-2019, 12:42 AM Thread Starter
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Do you have an ada amazonia substrate too? I've heard it can soak up phosphate. I just thought it would be full after three months of this...
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post #4 of 6 (permalink) Old 04-01-2019, 01:27 PM
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I'm running tropica soil. I've been thinking of increasing my dosing, but since I don't have any algae issues, I'm a little hesitant to make a change until I understand a little more what's going on.
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post #5 of 6 (permalink) Old 04-01-2019, 02:32 PM
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I am currently dosing 12ppm of phosphates weekly and my expired API kit reads maybe 0.25-0.5 ppm at weeks end with 6 month old Tropica soil. I too assume the soil is soaking it up, I havn't bothered to do anything except increase phosphates a couple times and watch the plants. Growth is mostly good so it hasn't bothered me much, nitrates test between 10-25 again with an expired API kit for what it's worth.

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post #6 of 6 (permalink) Old 04-01-2019, 08:05 PM Thread Starter
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Hmm sounds like a wider issue that newbies should be made aware of. Like I said, when I was targetting only 1ppm, it would drop to nothing the next day but I wouldn't dose until the day after that because that's what EI suggests. This led to algae blooms for me.

Dosing every day to keep it at 5ppm solved the issue for me.
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