ray-the-pilot

How do you know your plants have CO2 deficiency?

Minsc

It varies from species to species. Rotalas will often become stunted and not display good coloration.
Toninas develop necrotic tissue and melt, especially the expensive ones

From what I have seen adding CO2 to the water is only half the story though. Without a decent rate of turnover, and a well layed out flow pattern, it is possible to have enough CO2 in the water column to kill fish, and still have carbon starved plants.

Minsc

On the topic of pH controllers:

The main benefit of a pH controller that I can see is that it will change the amount of CO2 added to the tank based on demand. After a major pruning, there should be less demand, and the controller will add a smaller amount of CO2. When the plants grow in, the controller can add more CO2 to the tank in order to maintain a constant pH.

Whereas, those of us who count bubbles, if we don't manually change the bubble count according to plant mass, it is very likely there is a gradual shift downwards in the available CO2 as the plants grow in, and a spike after a large pruning. Does this cause any problems? It is quite possible.

So, using a pH controller certainly has benefits, so why not use one?
With a pH controller, the bubble rate is higher than if CO2 were run constantly. If there is ever a malfunction of the controller or the probe, the solenoid sticks open, or if the alkalinity of the tank goes up, the system may very well blast the tank with CO2 and kill all the fish. That shouldn't happen on a manual system with a good needle valve.

helgymatt

I think many don't use controllers because they are not necessary and its just another cost. I don't find much change in CO2 concentration after a pruning, at least a noticable one. I find the manual way to work fine and very simple. Once I set the bubble count, i will normally just leave it until the tank is empty.

Indignation

Great for you - perhaps. Great for others - How exactly are you leaping to that conclusion?

My house is very comfortable at 62. (I have a high metabolism.) and my tanks do wonderfully at yellow-green. (My plants have...a... high... metabolism? That can't possibly be right! ALL plants grow the EXACT same rate, and have the same uptake demands, no matter what conditions are!)

ray-the-pilot

I never said that my rate was right for everybody. I said it was right for me. How do you know that your rate is right for your fish and plants? Especially how do you know that it is right for your fish? Are they breeding?

helgymatt

You know when the rate of CO2 is right when the plants are growing well and when the plants are not negatively affected. Fish show CO2 stress easily by gasping at the surface.

The idea is to have as much CO2 in the water, without harming the fish.

Plants won't show a CO2 deficiency, they will just grow much slower. CO2 is often the most limiting nutrient (carbon) in a closed aquarium system and when it is supplied, as we all know, we se an increase in growth rate.

helgymatt

They were maybe making a recommendation based on you're tank size. All tanks will require different amounts, bubbles per second, or whatever you want to call it.

Sunstar

I wish my fish would stop breeding.... I am about to be swampped...