[wantsome]

I have a 38 gallon full of crypts and anubias. I'm using sand for a substrate and supplementing the crypts with seachem root tabs. I'm using a satellite led+ light fixture dimmed down.

The tank has been up and running for a month. I have 8 small tetras and 6 panda cory's.

I'm trying to figure out the cause of the brown algae. It's starting to take over.

Could too much biological filtration be causing it?

I'm using a Ehiem ECCO canister and it's full of biomedia.

I'm thinking the biomedia out competeing the plants for amonia and nitrite and the aglae is using the nitrates to out compete the plants.

Any sugestions?

The reason I suspect the biofilter is I just switched from hang on back filters and they didn't have as much bio media. Since I made the switch the algae has taken off.

 

[AWolf]

Yea, your tank is not cycled completely, so you have an excess of nitrites, most likely. Give it a couple of months, do a lot of water changes, and clean the algae by hand until it clears up. Diatom algae is ugly and frustrating, but it does go away once the chemistry in the tank settles. It is still a new tank, with new biomedia. You are basically cycling your tank with the fish in it. I would do large water changes weekly or smaller changes bi-weekly or you may lose your fish.

P.S. I would also say that root tabs are notorious for fouling up tanks unless they are placed very very deep in the substrate, and the plants are well established an have good root systems to utilitize the ferts. I'd stick to liquid fertilizers.

 

[Diana]

Diatoms are high in silica.
They grow best when there is a source of silica in the water.
Sand is such a source. While the sand is new, small amounts of silica come out into the water, and the diatoms eat it up and grow more diatoms.

Otos eat diatoms, but do not retain the silica. They poop it out. Then the waste is decomposed and the silica freed to be reused, making more diatoms.

To get rid of the diatoms I would be as diligent as you can in vacuuming the floor of the tank, and cleaning the filter to remove the Otos' waste. Also, hand removal of the diatoms can help. Not just break them off and let them drift and get caught by the filter, but actually taking them out of the system. Water changes will also remove the silica.

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Nitrogen cycle:

Proteins added to the tank (fish food) introduce nitrogen into the system. Fish and microorganisms eat the proteins and break them down.
Fish produce ammonia, and microorganisms that decompose fish waste and fallen food can produce ammonia.
Plants, algae and ammonia oxidizing organisms use ammonia.
Ammonia oxidizing organisms release nitrites.
Plants can use nitrites, and nitrite oxidizing organisms (Nitrospira species) nitrites. (I am not sure about algae).
The nitrite oxidizing organisms release nitrate.
Plants can use nitrate, and I think algae can, too.

When there are insufficient nitrifying organisms (ammonia or nitrite oxidizing organisms) then you will see ammonia or nitrite in the water. A tank showing ammonia or nitrite is not cycled.
In a planted tank, the plants are also part of the bio filter, and play their role in removing nitrogen in all its forms.
Algae also removes nitrogen.

tank is not cycled completely, so you have an excess of nitrates

This is false.
When there are plenty of nitrifying organisms then you should not see ammonia or nitrite in the water, but will see rising nitrates.
When there are plenty of nitrifying organisms then the system is cycled with respect to the nitrogen cycle.
Rising nitrates is a sign that it is cycled.

The nitrifying organisms will only grow to match the food supply. It does not matter how much bio media you have. If there is just a little bit of ammonia, then only a small bacteria population will grow. Microorganisms will grow on all the surfaces in the system that suit them. Nitrifying organisms thrive in high oxygen, dim locations. They will grow on all the filter media, and in most locations in the tank. Having additional bio media does not mean you have more nitrifying organisms.

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What else has changed when you changed the filter?
Better water movement? Perhaps this is circulating the fertilizers from the substrate tablets. Some sands allow quite a bit of water movement through the spaces between the particles. This might also stir up more silica too.

 

[AWolf]

DIANA: Yea, I changed it to nitrites from nitrates within minutes of writing. I get the 'i' and the 'a' mixed up. Thank you so much for stating the err of my ways, Diana. Did you copy my post as I was writing it? I think we all make spelling mistakes, but to post almost an hour later when it was already corrected, leads me to believe you are watching everything I write immediately. I've always loved to have someone watching over me, but really?

 

[wantsome]

Ok thanks for the advice. The silica from the sand makes sense. I'm going to switch out my substrate soon to Eco Complete. I've had two bags sitting around. I just like the look of Tahitian moon sand.

 

[Hoppy]

Diatoms are high in silica.
They grow best when there is a source of silica in the water.
Sand is such a source. While the sand is new, small amounts of silica come out into the water, and the diatoms eat it up and grow more diatoms.

If I understand plants as well as I think I do, and, not having any background in the science of plants, I'm likely not as informed as I think I am, then sand cannot be the problem that leads to diatoms. Plants, and algae both have to have their nutrients be in the form of ions, which are molecules broken up by being dissolved in water, so the cations and anions are separated. But, quartz sand is only barely soluble in water. The ions that plants and algae can use as nutrients must be silicate ions: (SiO4)2-. Only silicate minerals other than quartz are soluble enough in water to build up a significant amount of silicate ions in water. Otherwise, all of the water on this planet would be loaded with silicates.

I have looked at a lot of water company "water quality reports", and have noticed that quite a few of us have tap water with silicates in it. (I assume that water sources that are primarily from rain have virtually zero silicates, while water sources that are primarily from wells, have more silicates.) For more information see: Water quality information - What are silicates and why are they in water? | APEC Water

From that article it looks like there is a natural cycle, where algae use the tiny amount of silicates in the water to grow, which depletes the silicates in the water. That stops that particular group of algaes from continuing to grow. And, that explains why newly set up tanks, filled with fresh water from our water company, can get a big diatom bloom, but it goes away eventually. That algae is then consumed by the fish and the silicate is locked up in the fish bodies.