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INFO RE Ph SHIFTS/ REQUESTED CO2 INFO

Posted By: greg <gregandeileen@juno.com>
Date: Friday, 23 August 2002, at 5:38 p.m.

Well, this is the 6th day after installing the Pothos- I thought I would summarize "the battle" to stop the wild Ph shifts.

Before the Pothos, I had lots of natural gravel and rock (all uncoated), and used RO water. The RO water came out of the tap at 6.6Ph/0 GH/0 KH. I would add about 1/2 tbsp Recon 50 to get Ph 6.8/ GH 5.0/ Kh 3.0. Every few days the Ph would "creep" to about 7.0, due to all the raw rock in the tank, so I would add 4 oz of solution of RO water with 1/2 tsp Acid-Balance, all premixed in a 32 oz container for (8) dosings. Very easy, slightly acid, very clean, very little algae, easy watercare.

After I put in the Pothos, I added slightly more Recon-50, because the plants would need more cal/mag and trace minerals. I set the tank at about 7.0 Ph/6 KH/7 GH. About four hours after setting the plants and running the lights I tested the Ph- it had shot up t0 7.8! I tested two hours later, and got a Ph of 8.0. A 1 degree swing (10X the alkalinity) in 6 hours- biogenic decalcification, no doubts!

I will explain this simply- the "textbook" explanation even gives me headaches!

Plants need calcium (cal), magnesium (mag), trace minerals (little bits of "minor" minerals) and carbonate salts to grow. All of these together add up the the GH or "total" hardness. "Hard water" has a lot of minerals, softer water less. Harder water usually carries higher Ph values, softer lower Ph values.

Plants use fish doo, some minerals from the water, light, and CO2 (carbon dioxide from animals) from the air to build carbohydrates (leaf and stem-mass)through photosynthesis, and give off oxygen for animals. At night, in the dark, plants "respirate"- they "breathe" O2 and give off CO2. Some of the CO2 "rebonds" with mineral salts in the water.

OK, so far. BUT, if not enough of any of these is missing, there are problems. This can be caused by too much turnover of the water (forces the CO2 out of the water), serious lack of mineral and minor minerals, too little fish doo, or not enough light. It is easy to supplement fish doo (add fertilizer), inhance lighting (better bulbs/different fixture), add minerals or slow the flow of the filters, if possible.

The amount of dissolved CO2 in the water is the most difficult factor to control, if not balanced. If the plants have all the other factors, but are "choking" from lack of CO2, they devise a way to survive. They start "stripping" parts off the mineral salts to form their own CO2, so they can survive.

Good? Not really. This imbalances the mixture of mineral salts, and the Ph can skyrocket, high. Ph shifts of 1 full point (10X alkalinity)or 2 points (100X alkalinity) are not unheard of. This can cause serious Ph shock to the fish, and since ammonia is 10X more potent with a Ph shift of 1 degree, fish can die quickly if there is any amount of ammonia in the water.

So how to stop this? The truth is the problem is addressed so poorly, or in such heavy scientific terms, the layman cannot figure out what to do.

The usual advice is "add CO2 injection to the water". This DOES solve the problem- with enough CO2 in the water, you can carry a reasonable GH and KH (amount of mineral salts and carbonate salts) for the plants and the fish (the KH/GH salts will mostly all stay in the water) The problem is CO2 gear is pretty expensive and you have to be somewhat technically inclined to set it up right.

So, when the Ph shift started, I decided the tank needed more carbonate salts to go with the cal/mag/trace (the Recon-50). I added baking-soda (sodium bicarbonate) to raise the KH (the Gh was already at 6)to 4- more carbonates, problem solved.

Wrong. The plants now had plenty of mineral-salts and carbonates, but when I shot the Kh from 1 degree to 4 degrees the Ph shot to 8, and this was early in the morning when I had started with a Ph of 7.2. A swing of .80, right away with the soda, and the plants will probably push it further, although not as hard because of the added soda. Within an hour of the lights being on the Ph shot to 8.2- this is getting bad, fast.

So the answer is if you add enough minerals and carbonates to the water for the plants to achieve photosynthesis by forming their own CO2, you will have to murder your Ph! Sorry, some say "no problem", but most tropicals do best in moderately soft water (GH=3-5/KH=3-5/Ph =6.6-7.2)

So, you can't "feed the beast" to appease it without having a nasty Ph, what about starving the beast? I thought if the plants were LIMITED in the amount of cal/mag salts and bicarbonates they would have to slow their rate of photosynthesis, so the Ph shifts would be less dramatic.

Over a 3 day period I siphoned small amounts of water from the tank and added pure RO water, and I also ran a softening-pillow (removes mostly cal/mag minerals to soften water.) Yesterday, I finished the final adjustments. I had the water at Ph=7.4/GH=3/KH=2. This is medium Ph water with reasonable general hardness and slightly low KH, which is important for plant-growth.

I have also contacted some real pros. They have recommended when I vacuum/waterchange I add slighlty less Recon-50 but balance with a "trace" mineral formula. This will drop the cal/mag levels slightly, increase the trace minerals slightly, and hopefully increase the KH slightly. If the cal/mag are slightly less, in theory I can bump the trace elements and the KH (carbonates) up slighly to get the same total hardness (GH) and Ph. I will have to wait and see.

It has also been recommended I use a carbon-bound liquid solution in the water- this allows the plants to suck up the "liquid carbon" to form CO2 from the water instead of breaking up the minerals. The stuff is not cheap (about $8-10 US), but, like the "trace" formula, a bottle should last a long time, 4+months for the "trace" and about 6 weeks for the "carbon".

Will it work? I don't know. All I know is right now the tank is sitting at the edge of a cliff as far as Ph goes, a balancing act. Dropping off the cal/mag and adding the trace elements and liquid carbon should help to stabilize, and will be much better for the fish and plants.

The point is right now the water is at a medium Ph level, with very low amounts of mineral salts. If I can stabilize it further, I probably can push the Ph down to 7.2 (I hope so!) and increase the Gh to 4 and the Kh to 3. These are good levels for the fish (if kept CONSTANT!!), and the Pothos should do well.

The conclusion is this- with strong light, enough fish doo and minerals, plants will grow like crazy, if they have enough CO2. If you have higher turnover, the CO2 will drop, so you will have to find a balance of less minerals, lower cal/mag limits (in the GH) and lower carbonate (KH) limits to "brake" the plant-growth.

These levels will be low, and adding trace-minerals to less cal/mag should hold the GH and Ph at the same levels, but be better for the plants and the fish.

Adding liquid carbon should also help, because the plants will slow the stripping of the mineral salts, so slightly higher KH/GH rates may be attainable without the wild Ph shifts.

I am watching the tank, and if it holds at 7.4 over the weekend, I plan to move to phase "B"- using the trace minerals and liquid carbon.

It won't be that bad- I will be able to calculate the ratios of Recon50/trace and keep premixed in the fridge, very fast to add at a cleaning or waterchange. I will be able to premix enough to last several weeks. The carbon will be added every 1-2 days, but it is very easy to add in just a few seconds, because it is a liquid.

Some people really were confused WHY some of us had these crazy Ph swings after adding the plants. After discussing this with some of them, one fact has arisen. They don't see the swings because they 1) have weak lights, slowing plant growth or 2) have naturally very low Ph water, and although they may have never tested it, I guarantee thay already have extremely low KH/GH readings 3) They are content with their tank sitting at a Ph of around 8.0. This means they are carrying HUGH amounts of cal/mag salts and bicarbonates, so the plants will strip the minerals, but can't remove enough to cause a wild swing (although they still admit they see some!!)4) they have little turnover, a good number of fish, and just a few slow-growing plants 5) they have CO2 injection.

This Pothos grows as you all told me it would- at a viscious rate! I split a 6" one and potted it wrapped around the UF risers (goodbye risers) and they have grown about 1,5" in one week!

I have enough fish-doo, HO lights, and had enough minerals in the water, but apparently not enough CO2. So I will go to phase "B".

If I cant hold a reasonable Ph with reasonable amounts of minerals in the water, the plants will eventually stunt, or I must live with a very high Ph. I won't do this. Sorry, I trust all the PhD's of biology who wrote the books I have- most tropicals do best at a Ph of 6.8-7.2, and I think I would be happy at 7.2-7.4.

If phase 'B' fails, I will have to go back to a no-plant tank, or get a CO2 system going. If I do, I plan to add more plants, because I will be able to. I know, if plan B works, I won't be able to have more plants-the pothos grows so quickly I will sill be having to keep a careful eye on the water-chemistry.

I tried to explain water-chemistry as easily as I could, and in a few areas I took the liberty to phrase things in such a way "purists" might think I misstated facts.

The truth is when you try to simplify something so complicted you have to phrase the material in simplistic terms, which can put you into a "gray-zone"of absolute scientific accuracy.

There are a few of those areas here, but if the average reader can get a grasp of the Ph shift problem and solutions, without having to exacly know and understand the biochemistry involved, the purpose has been achieved. Now that the groundwork has ben laid, I will keep you informed of how phase "B" goes.

And for all of you who HAVE CO2 systems, PLEASE- write in and tell 1) what type equipment you have 2) the suppliers 3) was it all in a "kit"? 4) what it cost 5) are you using a timer and celenoid-valve for night shutoff? 6)where did you buy cylinders/ where getting cyliders refilled, at what costs 7) how long does the CO2 tank last 8) any regrets, anything you would change if you did it again? 9) how long have you been using the eqpt??

This won't take long, and some input from owners of this gear would be invaluable in the archives. Because of this, would the first person responding start a new thread bookmarket 'CO2 EQUIPMENT INFO", and others post to the same throead. In this way, the search-engine will be able to pull it up more easily for future readers/researchers. Thanks for the info- GREG


 

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