Hi all - been lurking for a while. As the title says, I have battled a persistent diatom problem in my high-tech 7.5 gallon since start-up, and was hoping you lovely people might be able to offer some insight
Iím also very confused about fertilization. Waffled a bit as to whether I should post this here or in the ferts section, sorry about that.
Also pardon my rambling as I try to fit all of the pertinent information, and everything that I have noticed over the past four months, into a single post. Let me know if you have any questions or need more info!
Imgur album with recent pics: https://imgur.com/a/TthGS
Iím sort of new to the planted tank world, and this tank feels like one big experiment with balancing ferts - lighting - CO2. It has been set up since the beginning of January, and cycled quickly with filter media from my first low-tech tank, but I have been arguing with diatoms all throughout. I know they can be an issue for a couple months after the cycle completes, but now I'm just frustrated and donít really know what direction to take with it, hah. My major source of confusion is lighting and fertilization. I donít understand whether I *should* be dosing ferts to combat algae, or not dosing ferts, as I have heard both stances. At first, I went with the former:
Up until the beginning of April, I had been using dry ferts; NPK & Plantex CSM+B, at about 1/3 the recommended EI dosages. The light (Finnex Planted+) was on for 6 hours a day, and CO2 came on and turned off two hours before. I had some dust algae, which did its thing and went away, but cyano and diatoms would just *not let up*. My plants were growing well enough, but the Ďalgaeí kept spreading. I did 50% water changes twice a week.
The tank was/is home to a single betta fish. Plants are rotala rotundifolia and s.repens. The feesh in question is fed two or three pellets once a day.
Parameters/etc. around mid-March -
Tank size: 7.5g
Lighting: Finnex Planted+, on for 6 hours/day
Substrate: Fluorite black sand
Filter: AquaClear 20
CO2: Pressurized CO2 at 3bmp-ish; turns on/off two hours before the lights. Iím using a fluval diffuser and bubble counter.
Fertilization: Seachem root tabs; 1/3 EI, dosage figured through rota.la. Macros and plantex 3x/week on alternate days.
Water change: 50% twice a week
Nitrate: at least 80 (was not expecting! Geez.)
But then I went on vacation at the end of March. For that week, I reduced the lighting to 3 hours/day (brought the lighting down over the course of a couple weeks, and adjusted CO2 as well), and the plants went without their daily dosing of dry ferts. I was expecting some horrible algae explosion, but when I got home, I had managed to kill off the cyano (yay!), and while I still had diatoms, they at least hadn't taken over to the extend I was envisioning. So now Iíve kept the 3 hour/day schedule, and am only dosing Seachem Potassium twice a week. The diatoms are starting to creep back with more enthusiasm, however, which has led me to writing this post
I think what I am mostly confused about is how to handle ferts and get these diatoms under control. When I was dosing at 1/3 EI and 6 hours of light, I had major issues with cyano and diatoms, but was trying very hard to just push through it, hoping everything would come together eventually. Again, I have heard that dosing excess ferts causes algae, and I have heard the opposite. So I feel like Iím missing something. Longer photoperiod + fertilize? Longer photoperiod hold the ferts? Maybe with 1/3 EI, it was still too much. Whenever I trim or replant the rotala, new growth has always appeared small and leggy - not very bushy at all. Is it a light issue? They donít look ďstuntedĒ as if it were a nitrogen problem. JustÖvery small leaves. This was also the case while I dosed 1/3 EI. Iím stumped.
Lighting: Still the Finnex Planted+, now on for 3 hours/day
CO2: 3bmp-ish; turns on two hours before the lights, and off one hour before
Fertilization: Seachem root tabs, 1.5mL Seachem Potassium twice a week
Water change: 25% weekly
Nitrite / Ammonia: 0
The nitrate:phosphate ratio has stayed the same for the last two weeks. Not sure if I should try to up the phosphate to 2.0, or decrease nitrate to 10 (10:1 ratio, am I doing that right?). I have one or two dots of GSA, but nothing too exciting.
Thanks for reading, and any + all suggestions!