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Discussion Starter · #1 ·
Hi all,

A while back I made a post about algae issues in my 10g planted tank (Help with Algae Bloom). One of the issues discovered was that my tank had high levels of phosphate (5-10ppm). That was 5 months ago. Since then Ive done a revamp of the tank because most plants were just covered in algae and decided to replace them with fresh plants. Everything but the substrate was changed but I added root tabs. The new plants seemed to do well for the first few weeks. I was still getting algae on the glass but after 3 weeks i think, I started noticing algae on the plants.

Fast forward to today, the plants have stunted and have coating of hair algae (i think) on them, with yellowing on the tips and some melting... This whole time the phosphates are still high but less than before at >2ppm but <5ppm (Im using an api test kit and can't tell if its right at 2ppm, it seems darker than 2ppm but defs not the blue of 5ppm). Is 2ppm high?
I've been stuggling to figure out where the phosphate was coming from because I use RO/DI water. So I decided to test my ro/di and what do you know it read ~2ppm in the tub but ~0.5ppm straight out of the unit. The TDS reading of the RO/DI water is 0-1tds so I dont think the filter membrane needs replacing.

So I guess my 2 questions are:
Are RO/DI units meant to remove all phosphates?
Are my current phosphate levels, although improved, still a problem?

Another thing I noticed was that I was reading an almost undetectable amount of nitrates in the tank. Thus I figured that a nitrate deficiency might be the imbalance not allowing the plants to grow and take up other things like phosphates and so started dosing flourish nitrogen.
 

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Not sure why you are focused on PO4? There are lots of things that cause poor growth and algae, but too much PO4 is generally not one of them. That is unless it is very, very high. Many high tech planted tankers like myself dose to keep PO4 in the 5 ppm range.

Having zero NO3 is a much more likely cause.

RO water should not have any PO4. It appears your tank is generating PO4, likely from fish waste and feeding.

But in the bigger picture, if you really want help, you should list as much information about the tank as possible, along with some pictures. A holistic approach works best.
 

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Are you testing what is coming out of your RODI?

What kits/meters are you using?

The above advice is good....algae is an imbalance.

Most tanks go through an algae stage in the beginning but once plants are established if conditions are right their growth and nutrient uptake will outcompete the algae.
 

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Discussion Starter · #4 ·
Not sure why you are focused on PO4? There are lots of things that cause poor growth and algae, but too much PO4 is generally not one of them. That is unless it is very, very high. Many high tech planted tankers like myself dose to keep PO4 in the 5 ppm range.
Yeah true, I guess because prior to the rescape, I did have really high PO4 (Somewhere between ppm-10ppm) that never seemed to drop. But what you're saying answers my 2nd question too, that my current PO4 shouldn't be the problem (I read somewhere that 0.5-1ppm is ideal hence why i thought it would be a problem).

But yea as I mentioned I figured the 0 nitrates was more of an issue and have started dosing nitrogen, so that the plants might then be able to take up more phosphates as well.

I guess the PO4 in my RODI is a separate issue then.
Are you testing what is coming out of your RODI?
But yes theres 0.5ppm PO4 straight out of the RODI unit and around 2ppm in the RODI water in the tub. This is just annoying I suppose as I the whole reason I got an RODI unit was to have pure water that I have more control over.

nevertheless here are the tank parameters as requested:

PH: ~7-7.2
Am: 0
NO2: 0
NO3: 0 (but after dosing, im getting around 5ppm, is that enough?)
KH: 1-2
GH: 7
PO4: Somewhere between 2ppm and 5ppm (closer to 2ppm side tho)
Temp: 24C
CO2: None
Lights: 8 hours (inc. 2 hr ramp up and down) (10am-6pm). In addition to dosing nitrogen I also increased the light intensity and duration. For a while I have had at half intensity and 5 hours duration in the fight against algae but it did no difference. The reason I raised it back up this week was because for the first year of having this tank that was the lighting schedule and intensity I used and had no problems. I was even able to grow a lush carpet of Monte Carlo with no CO2 and no dosing at all. I figured if the plants were growing fine back then with those light settings, then its probs not the lights that was the issue (as pointed out by someone in that original thread I linked in the first post).

More likely a depletion of nutrients (aquasoil more than likely depleted too). With the rescape I also added root-tabs to the substrate. But since that was 4 months ago, Im thinking maybe that its time for me to resupply root tabs to the substrate.

Most tanks go through an algae stage in the beginning but once plants are established if conditions are right their growth and nutrient uptake will outcompete the algae.
This scape is 5 months old now (tank on the whole over 2 years), and plants were growing quite well but I was still getting quick algae buildup on the glass (~3-4 days after each clean). Although the plants were growing well and fast, I was also noticing algae on the leaves at the same time. Eventually the plants stagnated and Im pretty sure its because theres too much algae on the leaves. New leaves dont have algae but eventually succumb to it.

Also here are some pictures!
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Discussion Starter · #6 ·
Yes good idea just to be 100% sure and so that I know what 0ppm PO4 looks like in the vial (or whether my test kit is faulty)
 

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Discussion Starter · #7 ·
So I managed to get a hold of some demineralized water not distilled water. Couldn't find distilled water anywhere at the moment (we've recently gone into lockdown where I am) but from what ive been told remineralised water should have 0 phosphates as well? correct me if that's incorrect. Either way I tested it for PO4 and I'm pretty sure im getting a 0ppm reading. I'll attach a pic.
Table Liquid Drinkware Fluid Rectangle
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So I managed to get a hold of some demineralized water not distilled water. Couldn't find distilled water anywhere at the moment (we've recently gone into lockdown where I am) but from what ive been told remineralised water should have 0 phosphates as well? correct me if that's incorrect. Either way I tested it for PO4 and I'm pretty sure im getting a 0ppm reading. I'll attach a pic.
View attachment 1033350 .
Yes, DI water should not contain any phosphates, so I would take the pictured colour that you have as 0 ppm.
 
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