Planted FW tanks, substrate, pH and CO2 questions ..
 

I should ask this on a FW forum but what the heck let's put some activity in this one .. :lol:

I have a planted FW tank, must be coming up on 5 years old, and there's something I've never really been able to understand with this stuff.

I inject CO2 to try to have better plants than algae. For the most part it does not work out. For one, I can't seem to lower the pH of the tank .. at all .. with CO2. In fact, the pH is much higher in the tank than the tapwater is coming out of the tap.

Tap water is around 7.5, the tank runs around 8.5. This is with about 2 bubbles per second CO2 into a cyclone style CO2 reactor inside the tank.

Could the substrate be the cause? I have a mixture of black flourite and a laterite based substrate. Looked like crushed lava rocks though, if that helps.

A couple pieces of mopani driftwood are also in the tank.. could that be helping push the pH up?

I have a couple TLF phosban reactors kicking around somewhere, would it be a good idea to add peat pellets to help bring the pH down? If I do that, how do I know how much CO2 to add to the tank if I aim for a pH target based on the carbonate hardness of the water? (Or would peat bring the KH value down?)

I'll be doing some reading tonight in an effort to wrap my brain around these questions but I'd totally welcome any insights from planted tank gurus .. please and thank you!

What are you using for a co2 reactor (inline/in tank)?
120 bpm in what size of tank?
how much light?
What are you using for filtration ( canister/hob/sump )?


The substrate (fluorite/laterite) won't be the issue and I doubt the dw would affect it much...

I would check all your filter outlets and make sure they are well below the water surface. If you have a lot of surface agitation, lower the outlet even more or fill the tank up more. Are you using a co2 drop checker with 4 dkh water and ph solution to measure the co2 levels?

Ph is also very high for me out of the tap. I use a ph controller to drop my levels down to 7.0 which gives me about 30ppm. I also have lots of circulation throughout the tank (two canisters on my 90). Are you running the co2 on a timer or a ph controller? If you want a ph controller, I can trade you a milwaukee unit for one of those tlf reactors. :wink:

Not sure why the ph is higher in your tank. Do you have any limestone in there? That would definetely do it.

Thanks for the thoughts guys.. I don't have any limestone though. Yeah I did some more reading and came to the conclusions that neither the substrate or driftwood could explain the high pH. The only thing I can think of is that this tank kind of dropped off my radar for a while and I didn't do waterchanges for a long time (several months) and in the meantime just topped up, so maybe it's been building up for a while.

I kind of kicked my own butt into gear over this over the holidays and have been vaccuuming and waterchanging like crazy so I would have thought by now the pH would be closer to the tap water going in, but maybe I have more to go.

Is filtering through peat a good idea?

I'd take you up on the trade if you like, I don't have a pH controller but I do use a Milwaukee pH meter for checking pH. It's probably due for a probe replacement but I don't think it's shot seeing as I get plausible (and different) readings on other things so I think the >8 pH is probably correct.

So being without a controller, I just set the bubble rate to be reasonably steady and I watch what it does to the pH. When I first started injecting CO2 I found some chart online that matched target pH's to KH readings so I would just find a bubble rate that got me into that ballpark. I'd just increase the bubble rate right now except that I don't see any evidence it's pulling the pH down so I'm not sure what to do.

The tank particulars - 65g, has a sump, bioball tower. The CO2 is from a 20lb cylinder, the regulator and bubble counter are Milwaukee brand, and the reactor is a Red Sea cyclone mixer (this thing) .. I want to eventually upgrade to one of these.

Lights are 4x39w t5's, although I have 2 of them turned off for the moment until I get things straightened out.

I did have a Tunze 6055 for extra circulation in there but I've taken it off for now too in case the agitation was causing the CO2 to gas off out of the water too early. Although it hasn't made much of a difference so that's probably not it. I have a bunch of small tetras though and they seem more comfortable without that extra flow so I might keep it off anyhow. It was there for the loaches in there originally but they don't seem to be minding the lessened flow either.

The sump is your problem IMHO, you're gassing off your CO2...When injecting CO2 you really want to minimized your surface tension/agitation.

If you're looking for that AM 1000, they work excellent, I've run allot of reactors over the years and this one is by far the most effecient IME, I have a few of them, one is BNIB and can be had for half the price if you want it...I bought it for a new system build but then decided to try my hand at saltwater instead of another hitec planted system...

Filtering through peat moss would lower your pH. That's what a lot of discus-keepers do. We don't in the Lower Mainland usually because our pH is low and our water is "soft".

Also, as cale262 stated, reduce your overall surface tension and flow in the tank to allow the CO2 longer time to work in the water column before being dissipated into the atmosphere.

A lot of us locally are using Metricide instead of CO2. Its a concentrated form of the "plant food" Flourish Excel (double the strength) that is used to sterilize stuff in the medical field I believe. There's a local source for Metricide and its about $20 for a gallon which will last a very long time. I manually dose Metricide twice a week and the plants grow like crazy on it.

Anthony

And this metricide eliminates the need for injecting CO2 then? Interesting, will have to read up on it. I thought the whole point of CO2 is that most plants aren't meant to be submersed 100% of the time. I thought you couldn't compensate for that with more fertilizer or plant foods.. :neutral: ..

I guess what I'm not explaining very well is that what has me stumped is not that "it takes a lot of CO2." I understand I'm losing CO2 due to the sump. What has me stumped is that no amount of CO2 makes ANY difference.

Let me explain - in the past, although it took a lot of CO2 to lower pH, the CO2 DID lower the pH, there was a measurable difference between CO2 on and CO2 off. Currently what is happening is that it doesn't matter how much I add, it makes no difference to the pH. The equipment hasn't changed (same reactor same tank, just a different point in time). I was just trying to seek out potential causes for this change and thought maybe it was because the carbonate hardness seems inexplicably high as well.

I've even reduced the surface agitation quite significantly by removing the Tunze and it made no difference.

Unless I have a cylinder of just raw air and not CO2 maybe, but it was filled from the same fire extinguisher refill place I've used for the past decade so I have no reason to suspect that this is the cause.

PS. Cale I'm sending you a PM..

The Metricide goes through some sort of chemical reaction that releases carbon and reduces organic buildup in tanks.

If you check out how much to use of Seachem Excel, then half that dosage when applying Metricide.

Hey Tony, I have the same Red Sea co2 reactor and it does a very good job. But you have to keep it clean which means washinging it out every 3 weeks. Since you haven't done a water change for a while, i'm sure it's efficiency has been minimized.

Actually, a lot of plant people are moving over to sumps. You do have to crank up the co2 a bit but it should still be measureable (unlike your circumstance). Tom Barr (estimative index - plant guru) has a thread on his site going about his own tank with sump. It's been doing very well and he has no problems optimizing the co2 levels.

I would keep that Tunze turned on, just don't point it towards the water surface. You just want enough surface agitation to move a few circles around. With your overflow, there is no need to worry about any scum build up.

How is your drip plate setup? Is the water tumbling into a filter pad and then dispersed via a drip plate?

I read up on the phosban reactor and it is too small to run GFO on a 120 gallon system. Unless you want to trade both of them. :lol:

I dose the full Seachem line up with the exception of Excel and Flourish Trace. The Excel is not as effective compared to pressurized co2. But is an option.

Try cleaning the reactor first. You can completely dissassemble the clear plastic part. the bottom round circle needs to be pulled off with pliers. You need to take the impeller out and give the motor a good rinse too. Then dial your co2 to 2 bubbles per minute. I like to put vegetable oil into my bubble counter verus using water. Refill your co2 drop checker/indicator and check with again in 24 hours.

Water flow and movement is very important. The more circulation the faster the co2 can spread. It sounds like you don't have a drop checker and are measuring with a test kit?