Phosphate Buffering

[Themuleous]

Hi all,

I’ve been keeping fish for a few years now and have never really got to the bottom of one question:

Does phosphate in a tank act as a buffer and if it does what affect would removing it have?

I’ve got live plants in all my tanks and am thinking of adding CO2 to help them along; however I also have a phosphate value of around 1ppm. If I add say Phos-zorb to remove this phosphate and also start adding CO2 would I run the risk of crashing my pH because the phosphate is buffering the system? The KH is stable at 3 with a GH of 5 and pH 7. I use RO water with added Kent RO right so the water I add is pH 7.

If anyone has any thoughts as to what affect this will have I would be interested to hear them

Cheers

Sam

 

[@ombomb]

Have a look through this thread: http/www.fishforums.net/index.php?showtopic=104737

 

[Themuleous]

Thanx for the info, will read it at lunch.

It seems to me like the whole issue of phosphate in a tank is something that no one really knows the answer to. The latest PFK mag has an article that says there should be no phosphate in the tank, but I’ve heard other people say it should be at detectable levels! I must admit that in my experience I’ve not had a problem with algae even if phosphate reads 1/2 ppm, way higher that some people advise! But I do have lots of the algae shrimp so that could have an effect I guess. Nitrate is off the scale in my big tank so that’s definitely not in short supply!

Does anyone know if the plants themselves produce chemicals to fight algae? Tannins or something like that?

 

[George Farmer]

Welcome to the Forum!

Only very high PO4 levels will result in additional buffering capacity i.e. >10ppm. This is the reason many pH buffering products will result in enormous PO4 readings.

1ppm PO4 is fine for most planted tanks. Personally I wouldn’t use PO4 removal at all in a planted tank unless the readings were very high and plant growth was very limited.

I am surprised by your water chemistry. Do you use 100% RO with just Kent RO Right to achieve KH 3 and GH 5? I used to run a similar set-up but found I could never get a GH reading with my kit due to the lack of calcium and magnesium salts contained within RO Right. Same principle with KH, the only way I could get reading was to add Kent pH stable. I’m also surprised that you read 1ppm PO4 if you’re using pure RO.

If your water is as you state then KH 3 will provide enough buffering for CO2 injection.

As for the nitrates and phosphates “argument” – my opinion, and that of most modern planted hobbyists, is that nitrates and phosphates are essential for healthy plant growth, that in turn prevents algae. Reasons for this are still not fully understood but my thoughts are that through allelopathy the plants produce chemicals that fight off algae. The more plants and growth there is the more allelochemicals produced – less algae. Allelopathy is still not fully understood either, especially in the aquarium environment but the principles certainly illustrate the point well that a healthy planted aquarium rarely suffers from algae. The pinned algae thread may prove interesting for you too.

The author of the PFK articles you refer to is very old-school. He has success with his methods that involve no addition of nitrate and phosphates to the water column (I am guessing the soil-based substrate and fish provide enough) so understandably does not wish to promote their use. Unfortunately his methods are equally old-school and in my opinion offer little relevance to today’s potential planted hobbyist. If only they got someone more forward thinking to write a series…………..

 

[Themuleous]

gf225,

Thanx for the welcome and advice, really helpful.

I can't say the water chemistry was deliberate! I started with RO water a year ago and using the guide that was on the side of the RO Right bottle was aiming for a GH up around 12! but as it turns out what I have is ideal, because ive moved into the soft water side of the fish scale and it suits them, well they look nice and colourful and are lively so I guess that’s a good sign. I actually recently got a new bottle of RO Right that had a different scale on the instructions, which made it clear that I'd not been adding enough when I first started. The original bottle guide was very confusing, having to convert US gl to UK gl and work down from the 40lt measures they used, but the water has been stable like this for months now to guess ill just keep doing what Im doing! If your interested I add 16ml of RO Right to 20lt of RO water and only use RO water, never diluted with tap water.

Not sure what the 1ppm phosphate is from, the tank is at capacity and the clown loaches and plec are about 4in each so that’s probably why. But if you say its fine ill leave it be.

What sort of nitrate level should I aim for?

I assume the KH and GH readings I get are correct, they seem about right given all the factors, but ive heard that some test kits can be a bit off, but the API KH kit is easy to use and gives a very clear reading. The GH reading is a bit more difficult to detect but ive got my eye in over the months, so pretty sure that is accurate too.

On a slightly different theme, have you got any advice with keeping small planted tanks? say 20lt? The plants just never seem to survive very long. I guess one problem it that plant light tubes don’t come small enough! I do use leaf zone once a week but don’t currently have an iron rich substrate just quartz gravel.

Thanx again

 

[George Farmer]

gf225,

Thanx for the welcome and advice, really helpful.

I can't say the water chemistry was deliberate! I started with RO water a year ago and using the guide that was on the side of the RO Right bottle was aiming for a GH up around 12! but as it turns out what I have is ideal, because ive moved into the soft water side of the fish scale and it suits them, well they look nice and colourful and are lively so I guess that’s a good sign. I actually recently got a new bottle of RO Right that had a different scale on the instructions, which made it clear that I'd not been adding enough when I first started. The original bottle guide was very confusing, having to convert US gl to UK gl and work down from the 40lt measures they used, but the water has been stable like this for months now to guess ill just keep doing what Im doing! If your interested I add 16ml of RO Right to 20lt of RO water and only use RO water, never diluted with tap water.

Not sure what the 1ppm phosphate is from, the tank is at capacity and the clown loaches and plec are about 4in each so that’s probably why. But if you say its fine ill leave it be.

What sort of nitrate level should I aim for?

I assume the KH and GH readings I get are correct, they seem about right given all the factors, but ive heard that some test kits can be a bit off, but the API KH kit is easy to use and gives a very clear reading. The GH reading is a bit more difficult to detect but ive got my eye in over the months, so pretty sure that is accurate too.

On a slightly different theme, have you got any advice with keeping small planted tanks? say 20lt? The plants just never seem to survive very long. I guess one problem it that plant light tubes don’t come small enough! I do use leaf zone once a week but don’t currently have an iron rich substrate just quartz gravel.

Thanx again

Glad the RO Right is working out for you. I just mix 50:50 RO/tap now, much less hassle (and cheaper) and my tap contains a lot of beneficial nutrients for the plants.

Reading your signature I'd also say the 1ppm PO4 is from your bio-load, quite a lot in there for a 20G!

What is your NO3 reading at present, I'd assume that with the mentioned bio-load then it would be at least 10ppm or higher? In my experience a ratio of 10:1 NO3 to PO4 is ideal.

What's your lighting and planting out of interest, are you having success with no CO2? Any algae, nutrient deficiencies or stunted growth?

Nano tanks (less than 30L) require a fair bit of lighting relative to larger tanks. The Watts per Gallon rule doesn't apply and you need far more light than you may imagine. Check out this link - http/rexgrigg.com/./mlt.htm

CO2 is a must for well-lit tanks.

 

[Themuleous]

I might give RO/tap water mix a try, as you say would be cheaper, lots! My only concern is that last time I checked the phosphate value of the tap water it was up around 2ppm, and before I used RO water it resulted in tank being over 10ppm phosphate, with a huge algae problem!

Your probably right about the bio-load of the tank, I will be getting a much bigger one to accommodate the clown loaches and pleco once I move house, hopefully in the next year or so.

NO3 is difficult to read on the test kits, but it is at least 40ppm, probably more like 80ppm, unfortunately. I’ve read that high NO3 can damage plants and cause them to get holes in their leaves, would it be a good idea to bring this down?

Don’t think I have a lighting problem, as have three 18w bulbs, two of which are flora max plant growth ones, so am well over the 2WPG you recommend. I have also been using CO2 for about a 6weeks now and haven’t really noticed a difference in the plant growth, but algae isn't a problem. Just give the glass a bit of a clean every 2 weeks to remove any build up.

One other question, should I have LOTS of plants, I have 2 medium size Amazon swards, a single Echinodorus 'Ozelot’ and lace plant (which is suffering from lots of holes), should I add more?

Also, how do you clean the gravel when it’s got a covering of plants? I though a gravel siphon was a must to keep in from going anaerobic?

Ill give the light a go in my small tank, just added CO2 to that one mainly to bring the pH down but guess extra lighting would help too.

Cheers for all the advice