Plant Maintenance Advice

[darkdep]

Heating the substrate?  How do you do that?  Some kind of heating cable?

[darkdep]

FA:  That's what I was originally thinking...I understand the production parameters, and understand it needs to dissolve (and simply liked the looks of those little ladders)...but I wonder if that's all you need to worry about?

[Flawed_Artist]

I edited a post or two above. Basically, with a lighting ballast, but I once had 16 tanks running, so I used those tubular steel stands that could fit a tank on the bottom of the stand. With that, I just kept as much electrical as possible near the bottom of the substrate of the tank above. It only heated it a little, but I swear, best growth I've ever seen. I was using an NPK fert, iron and micronutrient ferts, substrate ferts, CO2, and I was also dosing with a bit of baking soda for good measure. This was the deciding factor, without a doubt. I guess it sped up metabolism? I don't know. It worked.

[Flawed_Artist]

My understanding is that the most overlooked issue with CO2 is stabilizing the pH in the canister. The chemical reaction that the yeast puts out drops pH quickly; baking soda helps to stabilize this. Otherwise, I believe that the temperature has to be lukewarm, and that's about it. I used a ten gallon powerhead, on a weird angle, aimed at my bubble counter ladder, to disperse the CO2 more, as it dissolved from the ladder's bubbles.

(Wow, that was a painful paragraph.)

[kennyman]

Once you get the fert regeme going you can check your co2 durring peek growing hours to see if it has become the limiting factor to growth. Then decide if you need co2. But right now your nurtient levels will be what holds your plants back.

[darkdep]

Thanks for the help everyone.  I'll get some ferts going and keep reading about CO2.

At this point, I have no idea how I'd put CO2 in the water and maintain a high pH for the Africans...

[BigDaddy]

If you want to do the CO2 route... buy the ladder for $15 bucks and you can make your own generator with yeast and sugar and a 2 litre pop bottle.

Google it... there are plenty of designs out there.  No point in you spending $20 plus dollars on a pretty can that can be replaced with a 2 dollar bottle of pop.

[darkdep]

Ok, that's what I wanted to know...if the pretty can had some advantage over the pop (which has a bonus, I get to drink it).

[Toss]

It is just prettier and cost you more money. I use 1.5L bottle from water. It is stronger and smaller.

[darkdep]

Now, with a DIY Co2 setup, do you need to worry about how fast the Co2 is produced?

[kennyman]

As for the PH crashing from CO2, you need to understand buffering capacity to know about how that happens. And when you get it figgured out, can you explain it to me cause I don't get it :/

[BigDaddy]

If you follow the standard receipes on the Net, then you shouldn't have issues.

As far as pH crashes go... here's the deal

Alkalinity (commonly referred to as kH) is a measurement of a volume of water's ability to resist pH change.   Simply put, the reason why soft water is easy to make hard and hard water is not so easy to make soft is simple; soft water has little to no alkalinity, hard water is full of it.

Alkalinity acts as a buffer (another term you'll here).  The higher the value, the bigger the buffer you have (the water's ability to resist pH changes).

When you inject CO2, you will be lowering the pH of the tank water.  The "potential" danger in this is that if you have very low alkalinity (less than 3 degrees of kH), you don't have a great deal of buffer, and you could experience a pH crash (where the pH drops dramatically, well beyond what the CO2 alone would do).

Now, I say potential in quotes, because I have been running an injected CO2 tank for the better part of 2 years and never had a crash.  All the while maintaining between .5 and 1.5 degrees of kH.

So, that's pH crashes in a nut shell.

Now... CO2 levels in the tank.  It is recommended that you do not exceed 30ppm of CO2 in a tank with fish.  It has been noted that fish exposed to those levels of CO2 will suffer, either in the short term by being lathargic, or "gasping" at the surface, or in the long term by compromising gill function.

Again, I've not experienced this myself.  I have run my tank with SAEs (which are very sensitive to oxygen deprivation) at 45ppm and never seen them up at the surface.  Of course, I might be the exception to the rule... but I can only go with my personal experience.

With a large tank, and a single bottle of DIY, unless your receipe was WAY off, it's unlikely you'll get those levels of CO2 anyway.

PS - The Hagen ladder is only rated for 20 gallons or less.  Anything more than that, and a DIY reactor is the way to go.

Hope this helps.

[Flawed_Artist]

What I have seen one person do is use T-valves - they're cheap and work well - to branch the CO2 tubing off, so you can run more than one ladder at a time. That way, the Hagen 20G ladder can still work. I'll check, too, but I thought that the CO2 canister from Hagen was the only one that was for 20 gallons or less - I got into an argument my  friend who branched his CO2 tubing off, because I didn't think that the principle that the ladder runs by would fail past 20 gallons, or change - the CO2 would always dissolve by the same means, and the more bubbles per second on it, the more absorption. Hagen set the 20 gallon value based on the CO2 output from their canister, I thought.

. . . I don't know what to think of this, either, but this was written in the Baensch Aquarium Atlas Vol. 1 - "At a pH value exceeding 8 the amount to dissolve carbon dioxide is negligible (after GESSNER)." (p. 32) It goes on to explain that ". . . the OH- ions are immediately fixed by CO2 and bicarbonate is formed." It basically expresses that CO2 seems to not have much effect past 8-10 pH.

Please, if anyone has contradictory info to any of it, teach me . . .

[darkdep]

Ok, all this info is great (and being absorbed, I promise!).  Ok, so I think I'm comfortable enough trying to build a generator and figure out the reactor deal (although I still like the look of that ladder, hehe).

I read a chart on a site that had a relationship between CO2, kH, and pH.  It confused me a bit...

I understand that kH acts as a pH buffer.  I am comfortable with that, as I have been adding epsom salt and baking soda to my tank water for a while now, and it has been keeping the pH and kH high (last I checked, which was a while ago, on one of my 30gals it was 8.0ph and 7kh...but I haven't measured my 90yet).

I also understand that CO2 lowers pH.  But, if your kH is high enough, will this still occur?  Or will the buffer absorb it?  I have read that 15ppm is the most "efficient" amount of Co2 to have going for plant growth, so that was what I was thinking of aiming for.  

I guess my desire is to have Co2, but keep my pH high.  Can I counteract the pH drop from the Co2 with more baking soda/epsom salt?  Will this have a detrimental effect on the co2?

[Flawed_Artist]

Without going into the chemistry, with 8 pH and 7dkH, you're ok, as long as you use that chart to monitor the amount of CO2 - I agree with BD - 30 ppm or higher, *usually*, fish don't do so well.

There's a triangular relationship between CO2, kH and pH. Higher CO2 levels lower pH, but your kH level is enough to buffer for a long time - probably about a month without water changing, at least, before a crash comes.

[darkdep]

Here's the chart I found:

The relationship of CO2 , pH and KH

Code Select Expand


-----------------------------------------------------------------------  
\  pH | 6.0     6.2     6.4     6.6     6.8    7.0    7.2    7.4    8.0  
KH\   | -----------------------------------------------------------------
0.5   | 15      9.3     5.9     3.7     2.4    1.5    0.9    0.6    0.2  
1.0   | 30      19      12      7       5      3      1.9    1.2    0.3  
1.5   | 44      28      18      11      7      4      2.8    1.8    0.4  
2.0   | 59      37      24      15      9      6      4      2.4    0.6  
2.5   | 73      46      30      19      12     7      5      3      0.7  
3.0   | 87      56      35      22      14     9      6      4      0.9  
3.5   | 103     65      41      26      16     10     7      4      1.0  
4.0   | 118     75      47      30      19     12     6      5      1.2  
5.0   | 147     93      59      37      23     15     9      6      1.5  
6.0   | 177     112     71      45      28     18     11     7      1.8  
8.0   | 240     149     94      59      37     24     15     9      2.4  
10    | 300     186     118     74      47     30     19     12     3  
15    | 440     280     176     111     70     44     28     18     4  
-----------------------------------------------------------------------
     |                 CO2  milligrams/liter -------------------------
---------------------------------------------- -------------------------

According to this, ph 8 and kh 6 is...1.8.  1.8 ppm, Co2?  Can someone explain this to me?

[BigDaddy]

Here's the scoop.

Your kH doesn't change... well not without adding baking soda anyway.

So, right now your tank is 6 kH.  In order to get to a meaningful CO2 level (above 15ppm), your going to need to see your pH drop to 6.8 or 7.

If you inject CO2, and your pH doesn't hit 7, then you either aren't adding enough, or its outgasing, keeping you from reaching "optimal" CO2 levels.

[kennyman]

If your stocked with hard water adapted plants do you still need to be concerned with higher co2 levels? Or can you rely on the plants specialzed abillities to obtain Carbon through the breakdown of compounds?

[darkdep]

BD, ok, that makes sense.  So, just so I understand the chart, another way to do it would be to increase kH, correct?  (i.e a higher kh would also allow meaningful levels of Co2?)

[BigDaddy]

No... adding kH does not increase CO2.  That's a common misconception.

When you add kH, pH goes up.  So the CO2 value remains the same.

6 kH 7 pH -18 ppm CO2

up the kH to 7

7 kH 7.1 pH - 19ppm

Adding the extra baking soda will make the pH go up - but the CO2 value remains a constant.

The only way to increase CO2 levels is to dissolve more CO2 into the water.


PS - Don't bother with the double or triple ladders.  A powerhead/gravel vac DIY reactor will cost you much less, and be a MUCH more effecient setup than the ladders ever could be.  Reactors will always be better than diffusers (which is what the ladder is)