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3 Posts
Discussion Starter · #1 ·
Hi I'm new here :)

I'm four weeks into my first planted tank setup since I was a kid.

My setup is as follows:

Osaka 260L Tank
Sand substrate
2 x 39w T5HO bulbs 3 inches above surface 7hr photoperiod
External Filter with spray bar
Powerhead with spray bar lower in the tank
Pressurised Co2 system
EI dosing (6grams of Potassium Nitrite, 1.5grams of Potassium Phosphate & 9grams Magnesium Sulphate per week) + Micro dosing
DIY root tabs in the sand

Current tank parameters:

Temp - 26C/79F
Ammonia - 0PPM
Nitrite - 0PPM
Nitrate - 20PPM
PH - 5.9 - 6

I have attached pictures of the issue I'm having with what I think are a type of Hygrophila. This is the only plant in the tank affected and it appears to not affect new growth. Up till now the plant has been growing great its grown maybe 9 inches in 4 weeks.

I hope someone can advise me to what I am doing wrong.


530 Posts
Based on your pictures, it looks like most of the damage is occurring on the old growth which suggest a mobile deficiency. So, it could be that you are not adding enough of either NPK or Mg.

I see many holes on the old growth which could suggest a lack of K.

How much of micros are you dosing? How much co2?

Sent from my iPhone using Tapatalk

3 Posts
Discussion Starter · #3 ·
I'm dosing Chelated Trace Elements 3 times a week totalling 1.8grams I believe.

My Co2 is around 3-4 bps the drop checker turns green.

Should I try increasing my macro dosing? or just up the K in my solution?

11,721 Posts
Aquatic Plant Central
I find this tool useful in figuring out fertilizer.

The other half is this:
Test results. When did you test the tank? Right after fertilizing? Right before? Mid way between dosing?
Can you also get tests for GH (General Hardness) and KH (Carbonate Hardness, also called Alkalinity)

If the NO3 in your test is from fish food (test was done right before dosing your once a week fertilizer), then the test is showing NO3 from fish food. The plants used up the KNO3 (and other ferts) soon after dosing. Fish food is also supplying a fair amount of phosphorus and most traces, but fish food is low in potassium, iron, calcium and magnesium. The deficiency could be from K, Ca or maybe Mg. It does not look like iron deficiency.

If the NO3 in your test is from mostly fertilizer (test was done less than 24 hours after dosing) then it is harder to say if the fish food is contributing so much, but still is adding some N, P, and traces. A test right before a water change would show if through the week these are getting closer to being used up.

The other question is: What is in the root tablets?

But your dosing program (based on information in this thread so far) is lacking calcium, and is a bit high in phosphates.

Here is what I would try:
Increase the dosing of KNO3 or add K2SO4 for more potassium.
Add a source of calcium so you are dosing Ca and Mg in a ratio of 4 parts Ca: 1 part Mg. Unless you have already tested and found your tank has a good supply of calcium, perhaps from the tap water. Most people do not, and simply add Mg because someone said to.

Test several times through the week for NO3 and see if you can find a trend that can help you figure out how much fish food is contributing to your tank.
In a high tech tank, with EI dosing the general recipe is to dose every other day macros, and the alternate days micros, with a 50% water change. Fish food almost does not count.

Here is the EI recipe from the fertilizer forum here at TPT. I have added a couple of comments in green text.
EI recipe for your tank size (260 liters = 67 American gallons). In most of these fertilizers there is pretty close to 5 grams in one teaspoon.
50% H20 change-weekly
3/4 Tsp-KN03 3x a week You are dosing only a little more than this much just once a week. Goal is 5-30 ppm NO3, and 10-30 ppm K. If dosing more KNO3 to get more potassium makes the NO3 too high, then add some K2SO4 to supply more potassium
3/16 Tsp-KH2P04 3x a weekIf you can get a phosphate test that would be interesting to see, but per the dosing tool I linked above, and because I know fish food has reasonable amounts of phosphate, I would bet it is high. Goal: 1-2 ppm phosphate, though I have seen higher values in my own tanks without problems.
1 Tsp-GH booster once a weekThis is not just magnesium, but a balance of calcium and magnesium in a 4:1 ratio. You are not just adding magnesium so your GH test turns the right color. You are adding a balanced ratio of Ca and Mg to make the right ratio in your tank so the plants have the minerals they need.
15ml 3/16Tsp-Trace 3x a weekDepending on what product you use, some trace mixes contain quite a bit of iron, others have less. I would not increase the whole mix just to get more iron.
4-8ml-Fe/Iron 3x a week Dose a separate chelated iron product if your trace blend is a bit low in iron. Iron is one of the first nutrients to get locked up in a way that plants cannot use, so once a week may not be enough in a high tech tank.

Based on this you are underdosing KNO3 (potassium is low) and overdosing KH2PO4 (phosphate is high).

The other thing I see is that the pH seems quite low.
If it is this way naturally from your water supply, or you are using reverse osmosis water then the water is not supplying several minerals: Calcium and Magnesium are the most important of these. Again, if all you are dosing is magnesium, without testing the tank for calcium, then you are probably adding too much magnesium and not enough calcium.

3 Posts
Thank you Diana for your in depth reply. Im new to all this so i'll do my best to follow what you have said.

When you say test for NO3 is that just the standard Nitrate liquid test kit?

The trace ferts i am dosing only contain:
Fe 8.2% (EDTA Chelated)
Mn 1.82% (EDTA Chelated)
Zn 1.16% (EDTA Chelated)
B 1.05%
Cu 0.23% (EDTA Chelated)
Mo 0.15%

There is no mention of any calcium? how would i get that into the aquarium?

The PH from my tap water is 7.4 but with Co2 injection it comes down to 5.9-6

i'll need to check for hardness but i only have the test strips for that.

As suggested i'll look at my dosing and try some fine tuning.


oh and i dose 3xmacro and 3xmicro per week and the root tabs are NPK 17 -9 -11 with magnesium and trace elements

I have ordered a GH and KH test kit to check my tank. Looking at the water data sheet from my local supply it says i have a german degree hardness of on average 1.8 and 9.96mgCa/l. So i must be lacking calcium in my tank?
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