I have no fish

[Iloveplants]

As some of you may already know, I have three planted aquariums with no fish. Virtually all of my plants are doing fine, but not thriving.

I am fertilizing frequently with liquid fertilizer and root tabs and just bought new and better lighting for one of my tanks so I'm supposing those aren't the lacking categories. But CO2?

I read somewhere that fish produce a lot of what aquarium plants need, is this true? I thought they just added extra nutrients but are they the main source of co2 for plants? I haven't been injecting co2 because I didn't think it was necessary, now I'm beginning to question that.

I have little intentions of getting a co2 injector just due to financial reasons as of right now but I am much more open to getting fish (I haven't had any in 2 years and miss them).

If fish can be the solution please do let me know, if not are there any other solutions that aren't a co2 injector?

 

[Aiken Drum]

Plants need nutrients, CO2 and light and will let you know if there is anything lacking. One of these 3 will be the limiting factor to a plants growth, so increasing any of the other 2 without increasing the one that is limiting will achieve nothing but algae.

In most aquariums with low demand plants the limiting factor will be light.

If you arent injecting CO2 then CO2 will get into the water from a variety of routes. Fish respiration is one. When plants arent photosynthesing they take in O2 and expire CO2. Gas exchange will occur at the surface and as CO2 is taken up by plants it will be replenished from the atmosphere, so an airstone or filter that gives good surface agitation will promote this gas exchange. Many of these low demand plants use carbonate hardness from the water and convert it to CO2 in the leaves. This is part of the process of plants transitioning from emersed to submerged growth as the plant adapts to use KH rather than atmospheric CO2.

2 essential nutrients that are provided by fish are nitrogen and phosphates. These can be supplimented with fertiliser, but most fertilisers have essentially zero nitrogen or phosphate because they are seen as promoting algae growth and are normally supplied by fish. In planted tanks that are lacking sufficient fish, or where they are very heavily planted and just use up more than the fish supply, there are fertilisers that do have a good amount of nitrogen and phosphate in them. NA Thrive is a good one to go for if its available in your location (America). We have TNC Complete here in the UK. Aquarium Coop make one and i think tropica do too. Aquarium Coop recommend 50ppm nitrate for healthy plant growth which i think is a bit extreme, but you do want some nitrate in a planted tank which these fertilisers will supply where fish dont.

 

[Caliban07]

You can put some potting soil under the substrate.

 

[Iloveplants]

Ok, thank you so much for the info!
Hopefully my plants will get better soon

 

[Chucker]

Cost for adding CO2 is not as bad as you would expect if you make your own with a 2ltr bottle yeast and sugar. The fish add more in the form of waste than CO2 to get a measurable amount of CO2 from them would be almost like putting a whale in a 20g tank