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ThriveC + Excel - Redundant? Algae/Diatom issues


AC Members
Soo I'm having issues with diatoms and some green algae on the walls of my 75G tank, I acquired this tank already established from craigslist, it was overstocked but I gave some fish away. Planted with anubias and some dwarf sags. I'm struggling with nitrates not going below 40 (might be higher), diatoms, and green algae. I started dosing some ThriveC. Later I was reading excel could help with algae issues, and I was thinking increasing plant growth would help decrease nitrates, so I ordered some, but I forgot ThriveC already has some carbon in it. Should I return the Excel or give it a shot, dosing both the ThriveC + Excel? Does ThriveC increase nitrates?



AC Members
I do not recommend dosing excel ever. It is a gluteraldyhyde (spelling?). Nasty stuff.

You can cut down on nitrates by increasing water change frequency and amount and lowering feeding. Algae can be caused by lights being on to long as well.

Thrive does contain nitrates so you could cut back on dosage of that as well. I dose once a week in my heavily planted tanks.

the loach

AC Members
I don't see the issue? Diatoms and green algae on the glass are signs of a healthy tank. It is just normal maintenance to clean it, though diatoms only need a sponge and the hard spot algae may need a razor.


AC Members
Alright I'm going to stop the ThriveC for now. It's currently a 75G with only two angelfish and I really want the nitrates down so I can add my schools of tetras - hoping to add 6 Red Phantoms and 6 Lemons. The diatoms are just unsightly, and a result of the high nitrates I think, although I just got a new scraper tool and that made cleaning it a lot easier this time. I just ordered some pennywort per the suggestion on another forum to help eat up the nitrates.


AC Members
Live plants are good for getting rid of excess nitrates. The only tank I have without plants (large cichlid tank) is the only one with diatom issues.


No freelancing!
Keep in mind that Thrive dosing is based on a heavier planting than what you have. Anubias are very slow growing, as well, and carbon is the limiting factor, but there isn't such as thing as 'liquid CO2' for aquariums. (Google liquid CO2, you will see pictures and understand why this is so). For the light planting you have, you likely don't need to fertilize unless you are going to add a bunch of stem plants and inject CO2.
My favorite read on Excel/Glutereldehyde, with the majority of the information (except for comments) from 2 folks who I absolutely respect in the hobby.


Normally, the 3 ways to remove Nitrates from teh wqater are.

Chemically, through adsorbing through a filter pad or whatever, which is seldom something I would consider.

Using live plants, and them growing successfully will use nitrates/nitrogen compounds as nutrition

or Water Changes which will put the nitrate level somewhere between where it is in the tank, and where it is from the tap.

Nitrates will come from

Being added chemically, like Thrive, or Seachem Nitrogen, or whatever aquarium fertiliser you use.

Being added through water changes if your tap water contains them.

Fish/Animals living in it.. it's a biproduct of using food, you said you were overstocked, and this can be related to the bioload of your tank.

It was a used tank, how well was it cleaned? any organic matter will add to nitrates also. I'd suggest a good cleaning of filter media, and gravel vacuuming of the substrate, check around any hardscape/decor to make sure there isn't something that really should be removed.

I'm gonna say that you should
  • Test your aquarium water, and your tap water.
  • list the contents of your aquarium livestock, plants, fish, size, etc
  • Share a picture of your aquarium so we can try to determine the actual plant mass that's in there
  • Describe your water change schedule, how often, and how big.
  • Maybe describe the equipment you are using, light especially
I would not worry about the diatoms, they should go away by themselves and are likelihood due to moving substrate around or changing it, which is normal even when moving an established tank. For the green algae, I would likely decrease the amount of light, put it on a timer and have a schedule where the light is on for maybe 8 hours a day, or 2 sets of 4 hours. make sure that there is no natural light hitting the aquarium, this will help plants or algae grow too, just the same as if you had a bigger light on top of the aquarium.

Hope that Helps.


Global Moderator
Staff member
I too got away from using Seachem's Excel, API's liquid CO2. I even used Metricide 14. I feel much better now that I got those extra toes removed. I read the above article and a bunch of other stuff after being prompted by some of our finer minds here on the board..

I don't keep plants/setups that require extra CO2 anyway.