Hello,
Im 2 week ago Im start my 80 gal tank. Im tried to made everything correct, using information which I accumulate since last half year and my biological past. - but faced with some problems and know trying to understand the reason. Hope here with help of you i can find right solution and start my tank.

So here my low-end spec:

80 gal (125х50х50). Small fraction gravel level 5-9 cm in front and up to 12 cm on the backside. No any fert or addition in gravel
Light T8: 1. Hagen SunGlo 30+Sylv GroLux 30+2x Osram 765 18 +1 energy safe 25 wt = so total 121 wt. Duration now - 6 hours/day
Co2 - from gas-cylinder - directly into pump inlet - 1-1,5 small bbl /sec
Pump - External Atman CF 1200 with expanded clay inside up to 1500 liter/hour , but I slightly dam flow(cause it made a lot of plant disturbance)
I install inlet and outlet (like Lilly pipe) in same end of tank - trying to made "flow"
Temp - now 23-24 degr.max
Plants mostly (Heterantera zosterafolia, hyhrophylla polisperma, bacopa carol, eleoharis acicularis etc)
No Fish at all
Water changes: - till now - 40-50% every second day (simply tap water with GH-11)
First two times tried to add some K2SO 4 after change but only slightly and then stopped cause of algae.

So on third day they came :-)
Its very similar to Rhizoclonium but I not sure - its smell like fish when take it out - and till now I tried to remove as much as possible, make water changes but its appear and appear on the all plants, on the graver, plants almost not growing, although made some pearling.
so actually I can not understand reason - Im trying to test No3 - 0. May be its because of unsteady nitric cycle? - may be another reason - please any suggestions

You don't have enough CO2 going into the tank. And, you need a way to measure how much is in the tank waterr, which means a drop checker, with 4 dKH distilled or deionized water and pH reagent in it. That will be green if you have about 30 ppm of CO2, which is a good target.

You have low light intensity, with only 121 watts of T8 light, so you could do the tank as a non-CO2 tank if you wish, but the plants need nutrients to be healthy, and healthy growing plants are the best way to avoid algae. With that light intensity you don't need the full EI dosing, but you do need to provide enough nitrates, phosphates, potassium and trace elements. For that size tank the economical way to do that is to dose potassium nitrate (KNO3), mono potassium phosphate (KH2PO4) and any one of several trace element mixtures. The first two you can order on line from Planted Aquarium Fertilizer or Rex's ferts

2 VaughnH
Thanx for the quick answer - so you think Im already should start dosing?
About light - in few days I will receive my 2 150wt Aquaarc MH lamp (10000K 9000 lm) and plann to use it in this aqua

PS and for this bloody algae - - whats the main reason of it ?