90 Gallon Low Tech Setup
I am currently having quite the difficulty setting up/ establishing my 90-gallon low tech tank. I initially set the tank up back in January 2019 but have not been able to get a handle on it. The tank is a 48" long x 18" width x 24" deep(tall). I originally used Seachem Flourite as a base then capped it with black sand. The filter is a Fluval FX6, the heater is a Finnex HMA-500S Electronic Controller Aquarium Heater, and I currently have the Finnex Planted + 24/7 (48") as my light. I also have a small piece of driftwood in the tank. I use the glass lids that came with the tank to help with evaporation and to help prevent the light fixture from getting water damaged. My goal was/is to keep the tank as low tech/ maintenance as possible using low light-demanding plants while trying to avoid CO2 injection as much as possible.
Initially, I tried using the 24/7 setting of the light fixture with some crypts, jungle vallisneria, java moss, and anubias that I moved over from my old 55 gallon low tech. However, this resulted in a slew of algae problems of various species and practically no plant growth, in fact nearly all of the jungle vallisneria and crypts died, the anubias are still just barely hanging on, but the java moss does relatively well. In addition, the only fish I were able to successfully keep were corydoras and malaysian trumpet snails. I have tried a variety of tetras, bushynose plecos, zebra danios, and RCS but to no avail. This led to me becoming disheartened causing me to neglect the tank.
Fast forward to December of 2019 and I decided to try again. With nearly all of my old plants dead, except for the java moss and some anubias and only the MTS and a handful of corys still around I performed a large cleaning on the tank- manual removal of all algae I could get, 50-75% water change, and changing all of the filter media. I changed the settings of the light fixture to be at max for 4 hours in the morning, a 4 hour off period, then 4 more hours on max in the evening, as opposed to using the 24/7 setting thinking the 24-hour run-time may have been contributing to my algae issues. I purchased a variety of low light-demanding plants such as Bacopa, Rotala Rotundifolia Red, Dwarf Hairgrass, Red Cabomba Piauhyensis Furcata Fanwort, Hydrocotyle Tripartita, Nesaea Pedicellata, amongst others. Also, under the assumption that the flourite may have been drained of nutrients by this point, I used seachem root tabs in areas where I had plants. This time over the period of a few weeks to months most plant varieties slowly melted away and died with the exception of some anubias, java moss, and some crypts. Again another algae explosion of a variety of types, but mainly hair algae. Also, the only fish I was capable of successfully keeping were cory varieties, MTS, nerites and this time amano shrimp also did ok, but other species such as tetras and bushynose didn't last. Over time most other varieties of algae except the hair algae subsided, but this may have been due to the large MTS population I have by this point (my guess is numbering in the hundreds- hard to tell since they're usually burrowed in sand during the day).
My pH remained at around 7.0-7.6 throughout this period (I would like this lower for tetras if possible), my ammonia and nitrites were always zero, and my nitrates were always under 20 ppm, usually under 10 ppm. The temperature remained at about 79 degrees throughout.
So as you can see I haven't had too much luck with the tank to this point. Currently, my thoughts/ concerns are:
1. The strength of the filter may be to blame for the fishkeeping considering it is a very large/ strong filter for that size tank, especially considering it has only one outlet. This may have resulted in stressing non-bottom dwellers out to the point of death. I plan to custom build a spray bar to help diffuse the flow over the tank and hopefully resolve this issue if it is one. Either way I imagine this is a good idea to help circulate water throughout the water column more easily.
2. I'm beginning to wonder if the lighting is too powerful on max for 8 hours a day resulting in the algae spurts causing them to outcompete my plants for nutrients and light. However, the lighting might be too low considering the plants aren't able to outcompete the algae, so I'm not sure which case is more likely. Also, I've always wondered about keeping the glass lids on the tank considering this can reduce the light getting into the tank and reaching the plants closer to the substrate. My guess is the light intensity is too strong as well as the photoperiod being too long so I may try dimming the light to 50-80% and reducing the photoperiod to one 6 hour period. I'd like to keep the lids on if I can to prevent evaporation and to protect the wooden canopy I have over the tank, it has gotten water damaged and mold in the past from evaporation. I'm also concerned the depth/height of the tank might be an issue with the lighting.
3. Are root tabs enough for low light root feeding plants so long as I add more every few months? Or would I be better off dosing liquid ferts, or a combination of the two? Like I said I would prefer the least maintenance possible but if dosing liquid ferts is necessary I will do it.
Any help/thoughts/comments/concerns/etc. would be extremely appreciated. I'm prepared to make one more attempt to establish the planted tank and purchase the necessary equipment (stronger lighting, smaller filter, etc.) if need be, but figuring out where my problems lie is my issue. My plan of attack is to manually remove all algae (again), followed by a 50% water change, cleaning of the filter, changing of the light intensity/photoperiod, and restocking of plants/ root tabs.
I know this is a lengthy post and I appreciate it if you read it and I'm sure there is some information I left out. If there are any more details on the situation that need clarification let me know and I'll be happy to provide them. Thanks for any and all help!