Phosphates, CO2 and Plant Growth

Discussion in 'Aquarium Plants' started by ryanr, Apr 11, 2010.

  1. ryanrModeratorModerator Member

    Hi all,
    Well it's been a while since I last visited, it's been a very busy 6wks.

    Anyway, I'm experiencing a small algae problem (green beard?) and started doing some research, and of late my Rotalas are losing their red colouring.

    Current Parameters as per my profile, with the addition that Phosphate is >10 (well off the scale).
    Light hours = 10hrs continuous per day (on timer)
    Temp is being reduced back down to 27C (80F), I had it higher trying to deal with ICH :( which resulted in the passing of my Blue Ram :'(

    LFS suggested that the loss of colour in my Rotala is probably a CO2 deficiency, and that low CO2 + high phosphates + good lighting = good algae conditions.

    According to this  , I probably do have a CO2 deficiency, and am now looking into a CO2 injection kit.

    I've just found a relatively cheap   that would be suitable for my tank, and wondering if anyone has any thoughts?

    I'm working on regular WC to reduce phosphates, and haven't tested tap water yet, but will test tonight, and may end up resorting to a phosphate remover (but can't fit it in my classic filter)

    My questions:
    What do people think about the CO2 kit? Is it overkill (I would like to add more plants to the tank)
    Has the LFS given me a load of ? (I generally trust the guy)
    Anything else I should be doing?

    note: I have Seachem Flourish tabs in the gravel, dose with Flourish liquid once a week, and dose with Excel every other day.
  2. ZenialValued MemberMember

    Algae can turn your Rotalas black and dead looking, but don't worry, give it a month and they will grow new pink/red shoots.

    Don't touch your CO2 until you've cleared the algae. That's the most likely cause as it's be smothered by the algae.

    Clean clean clean, keep those phosphates down and stave off your algae!

    Good luck Ryan! Keep us posted :D

  3. NutterFishlore VIPMember

    The guy at your LFS is steering you in the right direction. Anytime there are high phosphates in a tank the KH/PH charts become completely useless. The phosphates act as a buffer & throws the relationship between PH & KH out of balance. The charts only work in tanks that are buffered only by carbonates. Seeing you have high phosphates there's really no way to tell how much co2 you have in the tank. I'm not sure if the charts work with Excel either. I'll have to research that to find out.

    Assuming your tap water does not contain the high levels of phosphate, do several 25% water changes over the next week to get the phosphate levels down. If the phosphates are not from the tap then they are probably from overfeeding & dying/rotting plant material. Feeding less & keeping the tank free of dying plant matter will help reduce the levels along with the water changes. If the phosphates are from the tap then you will need to consider some other way of removing them such as a phosphate remover in the filter or I believe an RO unit should remove the phosphates.

    As for the Hagen co2 system I would pass on it. Essentially it's the same as a diy co2 unit. The only thing is that it comes with a bubble ladder diffuser. It still relies on the yeast/sugar fermentation process to supply co2. IMO you would be better served by making a diy co2 system for yourself. They only cost a few dollars to make & are cheap to run. You also have freedom to tweak it abit to suit your needs or to add more co2 generators to supply more co2.

    If your interested in building a co2 reactor for yourself have a read through these two threads: (link in third post contains photo instructions to make a generator)

  4. Nate McFinWell Known MemberMember

    IMO high phosphates do not cause algae...there is no need to have your phosphates that high though either. I believe the problem is from your lighting and Co2 levels which need to work together. Light intensity goes up, co2 needs to go up....light goes down, so does the demand for Co2. Here is a graph "Hoppy" from it shows PAR info at various depths for various lights. He is an advocate for getting rid of the watt per gallon rule which just doesnt work anymore with T5HO lighting and the like. Here is a link to the thread as well. Good read as well!


    So, currently you are not injecting Co2. Which means you should be aiming for around 40 micromols (low light on chart) With this method you dont go by WPG, instead you look for the type of tank you want to keep. It is based on 1 bul of T5ho, if you have 2 like you do you divide the target light by 2. So if you want to stay low light (40 micromols on the chart) you would aim for 20 micromols (since you have 2 bulbs)
    With me??? lol
    Follow the line over to where it meets with the T5ho green line and it will tell you how many inches above the substrate you should have your light. In this case your light should be around 30 inches above the substrate! Raising the light lowers the intensity.
    Assuming you add Co2 and are now aiming for medium light, say 70 micromols (divided by 2= 35) your light would need to be 18-20 inches above the substrate.
    I hope this all makes sense. This is not a perfect method but is much better than the watt per gallon method.
    Bottom line is, you have too much light for the amount of Co2 being added. If you add Co2 to match the lights you will also need to make sure you are fertilizing the tank or growth of plants will stop as well as bring algae. You also have the option of turning off one of the bulbs as well if your bulbs are on seperate switches or run independently.
    I would also cut back on time it runs from 10 hours to 8.
    I hope this makes sense and helps.
  5. NutterFishlore VIPMember

    Some good info there Nate. I agree that algae are not usually caused by high phosphate levels. Very rarely are nutrient excesses to blame. I've really only suggested getting the phosphate levels down a bit so that there can be a more accurate assesment of how much co2 is present in the tank. More common for algae to be caused by nutrient deficiency & even more common for it to be because of co2 & lighting imbalances or inconsistancy. I agree that in this instance the algae are most likely being caused by not enough co2 for the lighting that is being used. That's why I gently suggested the diy co2 rig. I figure that is always a preferably option to using less of the available light. :)
  6. Nate McFinWell Known MemberMember

    Your post was right on the money Nutter. There is no reason for phosphate to bethat high and will definately throw off Co2 readings.
  7. ryanrModeratorModerator Member

    Thanks Nate and Nutter.

    I knew one or both of you ;) would have the right answers.

    I've got CO2 kit on the way  , Nutter appreciate the DIY suggestions, normally I would do it myself, but I'm a fan of 'nice' looking equipment, and most of my DIY ends up looking like a dog's breakfast :;cr and for around $70AUD, I believe it'll do the job.

    Until I get a handle on it (never played with CO2), I'll stick to 'proven' methods. I also like the fact that it has its own diffuser that can be put on a timer :)

    I can always put a DIY reactor and mixture on later. BTW - [Nutter], in some of your posts/suggestions about DIY CO2, you suggest diffusing through the canister (put the tube into the intake strainer), wouldn't "air" going through the impeller potentially harm the impeller, given most canisters are a sealed unit and/or make the canister more noisy?

    Thanks again guys, appreciate the help. :;hf
  8. NutterFishlore VIPMember

    $70:eek: OUCH!!! For another $100 you could have got yourslef a full injected unit. For an extra $50 you could probably have gotten a second hand injected unit.

    Running the co2 through the filter might potentially shorthen the impellor life but in all honesty I've never heard of anyone actually experiencing that. I don't think it really matters that much anyway. Impellers are cheap compared to what we spend on the rest of our aquariums & thier maintainance. So it's no big deal IMO if an impeller only lasts 5yrs instead of 7-8yrs.

    With some filters the co2 can build up inside & then all get released at once. The sound is exactly the same as when you still have a little trapped air inside the filter after cleaning & that air releases itself. With co2 the bubbles releasing through the filter just becomes a regular rythm sound though & I don't actually mind it. Lets you know the filter is still working & that co2 is still being produced. I've only encountered the co2 build up with an Aqua-One canister filter before. With my Eheims the co2 is just going straight through as fast as it is produced & there's no extra sound at all. I also like using internal power filters to diffuse co2. They work really well. I've tried all the bubble ladders, bells, diffusion chambers etc & I still get the best results from using some kind of power filter as the diffuser.
  9. ryanrModeratorModerator Member

    Well, more so for Nate and Nutter, but here's a little update on my progress.

    The algae isn't beard algae, it's more likely to be thread or hair algae (easily removed, and looks like the photos I've seen).

    Anyway, I tested tap water, and it's free of phosphates, so I guess that just means I need to get to it with water changes [Melbourne water is so pure and great for aquariums], still above 10ppm atm, but i'm sure i'll get it under control. I have been busy haven't changed water this week (since Sunday)

    On the CO2 front, for the last 4 days, I've been dosing with Flourish Excel everyday at the standard rate (in my tank that means 1.5mL for 62 Litres), I haven't dosed any Flourish liquid [but still have Flourish tabs in the substrate], and have also been dosing 1mL per day with Flourish Nitrogen - why Nitrogen? because I have 0 Nitrate readings, and I believe after reading so much here, that Nitrates are required by plants, which FN is designed for?

    Given all this, it would appear that the algae growth has at least been arrested (I still have spot algae on the glass, but this is "healthy" isn't it - I didn't scrub on my weekend pwc)
    The Rotalias looks healthier (some red starting to come back on some bunches), my crypts are getting greener, and my unknown sword is brighter. And my moss is also growing faster.

    And whilst I can't explain it, my glowlights seem happier and more active - go figure ???

    My conclusions - this CO2 kit is definitely going to be worthwhile (given no water change, it can't be fresh water helping, and light hours haven't changed), and that my investment in time (researching) is going to pay off :) yay.

    Thanks to both of you, I might just get a successful planted tank going! :;toast
  10. NutterFishlore VIPMember

    The no nitrates doesn't surprise me. Plants absorb ammonia as thier prefered form of nitrogen. That leaves very little ammonia to be converted into nitrates. I could take a fair while & quite a few more fish before you start getting readings for nitrates in the tank. Here's a link about it that may interest you:  

    I'm glad it seems to be starting to all work for you. :)
  11. ryanrModeratorModerator Member

    Thanks Nutter:- interesting reading so far! I'll study it more when my eyes are more awake. lol :)

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