CO2, KH, PH and dying plants

[djlen]

Based on the information you've supplied, you are either gassing off CO2 in some way(surface agitation) or you're testing pH/kH is faulty.
If you intend to upgrade your lighting, I suggest that you go into the 2 - 2.5 wpg (CF) area, with a system that will allow you to add-on more light as you learn how to balance your tank. Take it slowly, rather than jumping into the 4wpg range.

Len

 

[robson]

For PH and KH measurement I'm using Hagen test kit. It could be that I didn't match the colour perfectly so PH could be down to PH=8, or theoretically 7.8, but not less.

Regarding a surface movement I can say that I have an internal filter that is creating some water movement and also an air stone, which can be considered that it disturbs the surface as well.

What should I do to minimise the surface movement? Should I increase the bubble rate? For how long would I need to leave the filter and air stone turned off to see the PH change and to prove that the problem is the surface movement?

I'm definitely going to upgrade the lighting in near future, just I have get some finance for that, because as you know the good lights are quite expensive.

 

[ashdavid]

Get rid of that air stone !, that is your problem, if you are concerned about oxygen in the water an air stone wont help you will get much more oxygen into the water column with healthy plants. An air stone is good for gas exchange which means you are getting rid of a lot of your co2 that you have just put in the tank.

 

[ashdavid]

Get rid of that air stone !, that is your problem, if you are concerned about oxygen in the water an air stone wont help you will get much more oxygen into the water column with healthy plants. An air stone is good for gas exchange which means you are getting rid of a lot of your co2 that you have just put in the tank.

I meant to say plants will get more oxygen into the water column than with an air stone.
Also read some of the stickies on ferts as well b/c you will need them to maintain heathly plants.

 

[lbritish]

I don't want to sound rude, but where do you get that information from.
1# increase the Co2 input and the ph will go down..

H2O + CO2 = H2CO3 an unstable chemical bond called Carbolic (or maybe Carbonic... do not remember the proper name for it) Acid. You may know this better as "Soda water". In the fish tank you add very little of this so it does not get fizzy like your soda but it is the same general principle. Obviously since it is an "acid" it goes lower on the pH scale the more you put in. By mixing CO2 with any water the pH will drop. The question is how much it will drop based upon chemical additives that lock the pH at a particular level. The only reason it will not go down is if you are inefficiently introducing the Co2 into the water column without using a device such as a difuser or a reactor or you are gassing off the Co2 with things like Spray bars, air pumps through air stones, or other agitation of the water that results in rapid gas exchange.

2# how do you increase the buffers without affecting the kh, buffers are carbonates or bi-carbonates which will dirrectly affect the kh

actually now that I look at what I wrote I totally screwed up what I was going for in that... TGenerally your fish like a particular GH which was not mentioned in the "test results". The KH with a few exceptions doesnt matter too much for many fish. What I meant to say was buffering the kH with well... hold on.... water chemistry google thing... here we go http://fins.actwin.com/mirror/begin-chem.html down around the altering water chemistry... Calcium Carbonate changes both... kH only is sodium bicarbonate...

Anyway my main point though is that most charts online are a little off when you get into the higher kH when you are trying to calculate the level of CO2 in the water and also that .1 pH can be a DRASTIC difference in CO2 concentration in some circumstances.

Regardless of accuracy of any of the other statements due to wording or scientific "weirdism" though there are 2 big issues with that tank. 1) Not enough light. 2) Inefficient dispersal of Co2 apparently into the tank.

To get a good idea of what is going on in the tank if we have the following in any circumstance anyone can give an educated set of guidance:

A) Dimensions of tank and volume
B) pH of water prior to the introduction of Co2 system
C) KH of water in the tank
D) desired GH for the tank
E) present GH for the tank
F) Light system on the tank.
G) Filtration on the tank
H) pH after you started CO2 on the tank

With those bits of information you can determine if the lighting is adequate or not and what the chemistry of the water will allow for CO2 and whether the CO2 is being mixed efficiently or not based on the observation of the plant reactions

Also regarding other statements about melting plants...

There are "susceptible" varieties of plants that will not be happy in hard water or in soft water... most plants dont like very acidic water... some grow better in neutral water instead of either end of the spectrum... If you need a particular pH then you need to make sure your plants match up or as I said they will "melt" or do other creepy things in many cases.

 

[RTR]

I believe that Tom Barr has identified a meager handfull of plants that do better in soft water; all the others, and all that are common in commerce, will do perfectly fine at any reasonable tap water KH/pH. Doing water mods for your plants is many times more likely to create problems than to assist in plant growth and health. Balance light, nutrients and CO2 and your plants will do well.

 

[ashdavid]

H2O + CO2 = H2CO3 an unstable chemical bond called Carbolic (or maybe Carbonic... do not remember the proper name for it) Acid. You may know this better as "Soda water". In the fish tank you add very little of this so it does not get fizzy like your soda but it is the same general principle. Obviously since it is an "acid" it goes lower on the pH scale the more you put in. By mixing CO2 with any water the pH will drop. The question is how much it will drop based upon chemical additives that lock the pH at a particular level.

The acid produced by this reaction "H2O + CO2 = H2CO3" is "carbonic acid", and what chemical additives did robson put in , none that I can see. What I don't understand is why you would say this,

If you need to keep it around 8.2 pH then you will have to inject a LOT more CO2 and buffer the tank upwards with a non kH involving buffer. In these circumstances the online charts and calculator resources are unreliable and death is likely due to too much Co2 suffocating the fish. Automated controllers also likely will not work well since you may end up with a chemically created pH that does not shift with the introduction of CO2 the same way as plain carbonate buffered tank.

If you did not put in a buffer, the kh would not be affected and therefore the ph will go down due to the reaction that you stated before by carbonic acid being produced from the co2 input. So assuming a Co2 level good for growing plants is 20 to 25ppm and staying in line with what you said of keeping the ph at 8.2 the KH would then have to be increased regardless of the GH, this is b/c as you may already know there is a direct relationship with kh ,ph and co2. Another point I would like to clarify is that the level of Co2 in the water column is not affected if the kh is lowered or raised, it will affect the ph but not the co2 level, it will always be constant assuming that gas exghange is not a factor.
As for your last statement about controllers, I will say that unless there is something in the tank like crushed coral, ph controlers are fine to use. The problem with crushed coral is that as it dissolves into the water the kh rises which affects the ph, which is therefore counteracted by the automated controller b/c it has been set at a certain ph and will continue to try to keep it there, this then means the co2 level will rise in a vicious cycle. I assume that is what you were talking about.

 

[robson]

I turned off the air stone an the air injection into the filter output and after 1.5 days PH is down to 7.6-7.4

So it was the reason. Silly me
I guess that now I have to check the PH and KH frequently to ensure that I wouldn't inject too much CO2 in the water and adjust bubble rate accordingly. Is that right?

I also wanted ask you one more question regarding the light. You measure the amount of light in wpg or wpl (watts per liter). But is that correct just for florescent bulbs, or for all bulbs. What I mean is that lat say energy saving bulb 20W should give same amount of light as ordinary bulb 100W. But in that case I don't know what wattage should I use as reference. I have feeling, that florescent tubes are sort of energy saving bulbs as well. So let say if I decide to buy powerful halide light. Is the formula still valid, I mean do I still need 300W halide light?

Thank you all of you for great help.

 

[robson]

Sorry,

one more question.

What brand and type of light would you recommned for my tropical tank?

 

[djlen]

Check your pH/kH relationship twice daily for about a week to be sure that you're getting the saturation that you want. I suggest checking at lights on and lights off.
You will note that at lights on your pH will be lower because the plants were not using the gas in the darkness. Some people turn the gas off at night for that reason. I personally do not, but leave it run 24/7 and show a very slight drop in pH....certainly not enough to warrant turning it off, IMO.
CF(compact fluorescent) is the lighting of choice for many aquarists. It is, again IMO, the most efficient for most tanks. The mid-range Kelvin rating (5500K - 6500K), to my eye is the most natural.
The wpg quotient applies for most lighting applications. Pay no attention to the 'energy saving/ordinary light bulb' sale pitch stuff. If it says 20 watts, use that as your yardstick.

Len