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Pros and cons and pros again of lots of plants: a disaster avoided!


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Last weekend, I got a lesson in both pros and cons of too many plants.

I noticed my 20g tall tank looked 'off' and couldn't figure out why. I sat there wondering what could cause the conditions I was looking at: the water looked 'thick' somehow. The normal sparse layer of duckweed on the top of the tank was very dense and when I disturbed it by moving a net around, it didn't immediately float back up. It rose slowly-- more like the tank was full of baby oil than water. There were a lot of dead and decaying leaves from my aponogeton drifting around like rotten seaweed.

The four fish in the tank looked okay and were behaving normally; I really could not understand how, because the tank looked so grisly and the pH was high.

Worried that so much duckweed might be preventing air exchange, I decided to check the airflow into the tank. The airstone was bubbling along as usual. But the filter was not 😞 

Between a giant anubias and dense corkscrew val blocking the view, the sponge filter was not visible from the front or side of this tank. I had been turning lights on and feeding every day but honestly could not say when I had last observed the filter.  My guess from the Armageddon look of the tank is that the filter had not been running for a couple of weeks or more.

With decreased surface motion, the duckweed layer thickened up and choked out light and air, despite a large goldfish living in the tank!

So: too many plants was bad because I couldn't see the filter to notice there was no air moving through it. But too many plants was also good because with two large fish (and two small ones) in only 20g, the fish were still alive and appeared unbothered by lack of airflow and devastation all around, because (I assume) all the plants were also putting out some oxygen and consuming some of the waste created by all the rotting leaves.

I apologized to the fish, got the filter running, removed the duckweed as much as I could, removed the anubias and a lot of valisneria, added an Aquaclear full of crushed coral to help with pH and catching floating crud, gravel vac'd and did a couple of water changes. It's still an example of  Armageddon Lite, but at least the water looks like liquid now. 

The moral of the story is: don't let plants block your view of your air sources, but if you have a filter failure, having a lot of plants may be a great advantage.

No photo of the tank because it's too humiliating!




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I am also glad the fish were ok! It's crazy how sometimes even when we think we spend adequate time with tanks how much sometimes we don't notice what's going on in there. A question I often ask myself when doing tank maintenance is "I wonder how long that's been like that?!". This can be in reference to good or bad discoveries. 

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