# Fresh water refugium question



## Jose (10 Oct 2014)

Hi all.

I just saw a video on a planted discus tank that had only had like a few water changes in years.
This tank has a refugium with a plant in it.
I was wondering the following:

The plant in this refugium is supposed to be generating components (metabolites?) just like it would be happening in a high tech tank, since its growing at a very fast speed as its not limitted by co2. This substances are supposed to be what drives us to do water changes so often (supposing here our ammonia is being taken care of by the filter). So what is happening to those substances that is not happening in a high tech co2 injected tank? Are they being consumed by the bacteria in the refugium? If this is the case..couldn't it be happening in our filter but not to the degree needed in a high tech. If we got to the point of balancing the breakdown of these substances to their generation, could we go the no water change route (I suppose this is the case of a low tech)? 

In other words, why wouldnt a tank with only floating plants need water changes and a high tech tank would? The plants are supposed to be growing fast in both cases. Maybe the immersed leaves are the ones generating metabolites and not the roots of the floating ones.

Link: 

Great video by the way.

I hope I explained myself there. Do keep in mind English isnt my first language.

Thanks in advance

J.M


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## EnderUK (10 Oct 2014)

Plantbrain (Tom Barr), has suggested you can reduce dosing EI and progressively reducing quantity until you get negative respones then bump it back up past the 'critical point'. However if plant mass increases then you'll need to bump it up again.

By reducing light you lower this critical point and slowing everything down, you can then reduce the frequency and amount of water changes required.

He does stress that water changes are always good for a planted tank and the process is quite long. If any problems arise it's better to go back to a richer dosage and increase water changes.

You can read more here.

Me I've switched from high tech back to low tech now and I still do my 50% water changes a week.


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## Jose (10 Oct 2014)

Supposedly water changes are not for removing the inorganic ferts which we are adding. They are for removing the substances that plants are generating due to their high metabolism in a high tech tank. I have done a bit of reading (I dont consider myself a newb) so I hope someone can answer my first question without trying to convince me of how important water changes are (I know how important they are). Dont mean to sound rude. I am not worried about inorganic ferts building up.

J.M


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## EnderUK (10 Oct 2014)

He does mention that reducing the frets is for those that don't like waste. It was more the point of reducing light that reduces the need for water changes. You can have a low light high tech tank with minimal water changes. I was using a low light high tech method but was having issues with my live stock so switched to low tech. Light is the driving factor.

Sent from my Radar C110e using Tapatalk


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## ian_m (10 Oct 2014)

Jose said:


> Supposedly water changes are not for removing the inorganic ferts which we are adding


Water changes, in high tech EI dosed tanks are for both removing surplus inorganic ferts as well as plant waste.

If you don't do frequent water changes, and as you are dosing EI in excess to what the plants need, eventually the ferts levels will build up to lethal levels for the fish. I have accidentally does 350ppm, way above the EI 20ppm with no fish issues. So with 50% water changes even if the plants consume none of your EI dosing, the levels will never build up to be an issue with the fish.

As you are running high tech the plants are also producing masses of organic waste, which if not removed, may lead to fish heath issues and algae.


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## Jose (10 Oct 2014)

Does anyone know if floating plants generate some kind of organic waste when photosynthesizing at high levels in the same way plants in a high tech tank do?.

Cheers

J.M


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## Jose (10 Oct 2014)

Hi Ian. If you say you dosed 350 ppm without fish issues.... we could go more than 15 weeks of EI dosing probably without ill fishes. I am not saying this would be the right way to go but this is telling me that the water changes are mainly for removing plant's and fishes' organic wastes, not inorganic ferts. But of course lowering back your ferts is going to be beneficial since they are not accumulating. In other words its not mandatory to do weekly water changes to prevent inorganic fert accumulation although its a benefit.

J.M


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## ian_m (10 Oct 2014)

Jose said:


> If you say you dosed 350 ppm without fish issues....


It was at this level only for a day or two before I realised my dosing pump was running 24/7 and had emptied 1 litre of macro into my tank. Long term effects on fish is probably not good at these levels.

Problem with not changing water in high tech tank is the organic waste from plants builds up very quickly and leads very quickly to algae, regardless of fish stocking levels. Often when I go on holiday for say two weeks, I end up missing two water changes. I find the tank has started to get algae appearing on the glass when I get back, especially at back of tank where flow is the lowest. Cleaning algae off and going back to weekly water changes algae does not reappear.

I have, when I remember/can be bothered, reduced the lighting period and dosing levels (via pump) when I have been away and found no algae when I have got back. Once went away for 4 weeks, with reduced light and dosing and no issues when I got back, plants no so deep green but no algae.


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## Jose (10 Oct 2014)

Exactly. Ive noticed same thing in my nano. Its all down to organic waste. Using activated carbon should get around this slightly shouldnt it?  So in the end having a high tech planted tank is a bit like having an overstocked tank in someway... it seems.

Cheers


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## EnderUK (10 Oct 2014)

You guys are still assuming that high tech equals high light. Read that thread I posted, Tom has some lovely high tech tank with low light which he does monthly water changes on. If you reduce the lighting you reduce the plant growth so reducing the organic waste generated by the plants.

Edit I'm not saying it is easy to do, Tom is a master at what he does.


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## EnderUK (10 Oct 2014)

Jose said:


> Does anyone know if floating plants generate some kind of organic waste when photosynthesizing at high levels in the same way plants in a high tech tank do?.
> 
> Cheers
> 
> J.M


To answer this, getting floating plants to work in a high tech tank is extremely difficult. Floating plants just melt in most high techs since you usually require a large surface flow which damages the roots, bends the leaves under the water and gets water splashed on top of the leaves which then acts as focal lens burning the plants. This melt then adds to the organic waste. There are a couple of methods that half work but you'll never get a great coverage.


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## Jose (10 Oct 2014)

I think I didnt explain myself clearly enough (my mistake). I dont mean floating plants in a high tech planted tank. I mean that floating plants (for example in a low tech setup) have a metabolism which is probably as fast as those of immersed plants in a high tech. This is because they are not co2 limitted and are near to the light. And my question was: Do these floating plants under relatively high lighting generate an important amount of waste in the same manner that the plants in a high tech setup do?

The reason why I am interested in this is because of the video which shows a self-sustainable setup. It looks like its not posible in a high tech whether its high light or low light because plants are putting too much waste in the system (Tom still does 50% a month). The plants metabolism is still fast in a lower light+CO2 setup.

It seems to me that no matter what goes into the tank in the video its being broken down by the bacteria in the refugium.

All my questions are being asked with a self sustainable discus tank in mind although I am aware that 99% of people are going to try and put me out of the idea.

For this it would really be helpful to know if floating plants are adding nasties to the system because, if they are, a refugium would be the only answer around it. If they are not then you would just need a big filter for your fish waste and good filtration+floating plants.


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## EnderUK (10 Oct 2014)

having watched about 20 minutes into the video (been at work with youtube block) I see what you mean.
You'll probably have to get a plant guy in here (calling Darrel) but I think basically that emerged plants (floating) will release the waste into the air. He did talk a lot about the NH4, NO2 and NO3 and the main purpose of the plants to take up the production of NO3 from normal filters.

I believe in high tech tanks that there is a large production of plant waste that then takes up oxygen which is used in the nitrogen cycle that breaks it. You then get excess NH4 and bang! algae and fish problems.

If you decide to use this method then you might need to increase CO2 injection just because sumps are another open gas exchange. I would still use rich dosage and big water changes and then use the Barr method of reducing both until critical point is reached.


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## Jose (10 Oct 2014)

Yeap it would be a low tech with floating plants so no worries about offgassing co2 in the refugium.


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## X3NiTH (10 Oct 2014)

I have an east facing indoor 2ft windowsill box with only floaters in it, L.Levigatum(Frogbit), S.Natans(Salvinia) and P.Fluitans(RedRoot), massive growth on nothing but top ups (no water changes) and an occasional skoosh of Tropica Premium, it produced about a half kilo of compacted surface plant mass when I came to thin it out, it had been in there the whole summer and it has left a good few centimetres of mulm on the bottom. A lot if this is probably leaves that when submerged by overgrowth are broken down and left to settle on the bottom but there's definitely plant waste in it as it looks and has the same constituency as the mulm I pull out the filter on my high tech.


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## Jose (10 Oct 2014)

Mmm quite interesting X3NiTH. I did have a bowl full  of lemma once and wáter was crystal clear and no detritus. But ofcourse this was a much smaller scale.

Also youd have to keep up with the dosing since fishfood might not have enough potassium or phosphates etc. This way the plants dont die generating more waste. But that would be fine with me.


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