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Discussion Starter · #1 ·
I've read that in a low tech tank, water changes are a bad thing because the new water has higher co2 levels and thus can trigger brown algae outbreaks. How come this co2 difference is not present when water is toped up on the tank? Also, isn't almost all the co2 present in the water degassed from the aggetation of getting poured into the tank?

Basically I would like to do maby one water change a month to keep the water clear and tannis down from the driftwood.

40 Posts
Discussion Starter · #3 ·
That premise is totally wrong. You need some CO2 in a planted aquarium and that doesn't cause brown algae outbreaks. Where did you read that? Brown algae, or diatoms, can be caused by stirring up the gravel, but will usually recede in a tank with sufficient lighting. Otocinclus will eat diatoms.
Tom Bar:
"Don't ask why, just do it if you want the issue resolved.

SAE's will definitely nibble and prevent it in non CO2 tanks if you stop those water changes.

Less work if your solution, seems weird, but it does work.

You can still do the no water changes and bomb with Excel also.

The water change flushes the tank with lots of fresh CO2 rich tap water.
This one time flux once a week favors the Algae, BBA likes slightly higher CO2ppms, around 5-10ppm seem optimal and flowing water.

Excel is a biocide at higher concentrations, like H2O2.
It's active ingredient is used for a number of things for this purpose.

It's selective and can kills fish and plants at higher levels and some species like Egeria.

I'm trying to get a test set up for it's selective usage for killing Egeria weeds but leaving the native species alone and enhancing their growth.

BBA will generally never grow in a non CO2 planted tank that gets no water changes, top off only.

Some folks have taken to changing their water late at night and then hopefully degased water come morning. Often it takes a little longer than 12 hours for that to occur, so they often still end up with BBA.

This is speculation, but it does make sense in the context of what is known about BBA and the method works and the hypothesis is supported by the many observations from folks over the years.

Something about what changes influences BBA, I know it's not the N, P, K, Traces, GH/KH, lighting(as long as it's suitable for a non CO2 plant tank).

So not too many things are left........
While some like to say I speculate, they do not offer up a better alternative hypothesis.

Plant density is one, you need a good well planted tank for this to work.
You also need a source of nutrients for the plants in a non CO2 tank, fish waste and soil/nutrient rich substrate can typically supply perhaps 80-100% of the nutrients, some plants will certainly benefit from KNO3/KH2PO4/Gh/Traces once a week or two or if you want to use inert substrates/lighter fish loads or the substrate is depeleted.

I've done both and they both are simple and easy to care for.
Dosing once a week, no water changes?
Is that(adding 2-3 things weekly) as hard as feeding the fish daily?

So you can do the entire non CO2 method with inert substrate and not a ounce of soil, but you have to make sure you add things to the water column once a week.

When you add Excel, 1-2x a week and more is required, CO2 gas, 2-3x a week is required and so on.

Anything that increases the demand for nutrients must be added in the same relative proportion, so more light=> more CO2= more nutrients and so on......

Same thing, different direction: less light=> less CO2=> less nutrients.

Tom Barr"
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