Twenty gallon low tech, set up 22 days ago, inert gravel with root tabs and a cheap clip light on eight hours. Everything is covered in a soft brown film, glass, plant leaves, even the heater cable. It wipes off with a finger but is back in two days. Is this the diatom stage everyone talks about, and do I actually have to do anything about it?
If you want it gone faster, otocinclus or nerite snails eat diatoms enthusiastically. Two caveats though. Otos are sensitive and a 22 day old tank often does not have enough established biofilm to keep them fed once the diatoms crash, so I would wait until month two or three. Nerites are bulletproof by comparison, they just leave white eggs everywhere.
Seconding the wait on otos. I lost three by adding them to a month old tank and I still feel bad about it.
One thing worth checking rather than assuming: if it is slimy and stringy rather than dusty, and it smells faintly swampy, that is cyanobacteria and it behaves completely differently. Diatoms feel gritty and come off in sheets. Yours sounds like diatoms from the description.
Gritty and no smell, so diatoms. Thank you for the tell, I would not have known to check.
Wipe the glass with a dedicated sponge or an old bank card right before your water change so it gets siphoned out rather than settling back down. Takes 30 seconds and the tank looks presentable for the week.
@krausen_line · 2mo ago · 3 replies
That is diatoms and no, you do not have to do anything except keep wiping the glass. In a new tank the silicates leached from the substrate and the tap water feed them, and once the biofilm and plants start competing they run out and the whole thing collapses on its own. Mine cleared at about week six.
The two things that make it last longer than it should: adding more light because the tank looks dirty, and doing huge daily water changes that keep resupplying silicate. Leave the photoperiod where it is.
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@springtail_stella · 2mo ago
I had absolutely bumped the light to nine hours because the plants looked sad. Putting it back tonight.
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@mat_mira · 2mo ago
The sad plant look at three weeks is usually the tank melting its emersed grown leaves, not a light problem. Give it another fortnight before changing anything.
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