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Journal Inert substrate 150 gallon challenge

  • Thread starter Thread starter hamfist
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Oct 5, 2025
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Southampton, UK
This 5'x2'x2' tank has been running for at least 10 years, but has been 100% a "fish" tank. Embarrassingly all plants were plastic. However, it does mean that the filters and inert sand/gravel substrate are biologically nicely mature. I am new to the forum so I thought I would introduce myself and the tank to the group.
Almost exactly 1 year ago I decided to try and turn this plastic planted tank into a properly planted fish tank. I had been having some success with planted small low tech shrimp tanks and felt I had the skills to convert this main family display tank to a properly planted tank as well.
So over the last year this tank has evolved considerably, as I learned more and more about fertilisers (which are expensive for this size of tank unless you use dry salts), lighting etc, etc. (After a year I still feel mostly like a beginner).The game-changer was a couple of months ago when I started CO2 injection and suddenly My success rate jumped massively. I still have the challenges of an inert substrate but the CO2 helped enormously.
Here's the tank as of right now
071025.webp
So I'll try and list some stuff .........

Tank - 150 x 60 x 60cm
Filters - 3 x Eheim 2217 canisters. All filled with Eheim coarse foam pads.
Substrate - a mixture of coarse sand and fine gravel. All inert, from around 1-3 mm grain size.
Water - RO remineralised with Salty Shrimp Bee Minerals GH+, to zero dKH , 5 dGH. 50% water change weekly.
Water column ferts - These are from a brand called Solufeed, which is becoming popular in the niche market of planted aquaria in the UK. THese are not aquatic-oriented but are very popular in the hydroponic growing sector here. Brainier folks than me on UKAPS have worked out the best products and right doses. I don't have a set of scales and am inherently a bit lazy about these things so I converted the recommended weights of ferts for my size tank into level teaspoons of dry salts. The tank is big enough so that I can simply dose dry salts daily (I do dissolve them in a jug first).
Macros - Solufeed 2:1:4 High K (https://www.solufeedshop.com/214-high-k-1-kg-18-p.asp) - 1/4 tsp daily, plus K2SO4 - 1/8 tsp daily.
Micros - Solufeed Sodium-free TEC (https://www.solufeedshop.com/tec-sodium-free-54-p.asp) - 1/16 tsp daily.
Substrate ferts - spot-injected boluses of aquatic compost where required.
Lighting - 2 x 120cm Hygger LED units. Currently around 20-30 PAR on the substrate using the Photone app on my iphone. Rising up to 80-90 PAR near the surface.
CO2 - FIre extinguisher system. Cheap regulator, solenoid/timer. Homemade horizontal Yugang reactor plumbed into a variable bypass loop in the outlet of one of the canister filters. Use of Hanna CO2 test confirms around 30 ppm CO2 throughout key lighting period. Tank is aerated overnight.
Temp - heaterstat 25 C
Livestock .......
  • 6" Blue Acara
  • 5" golden gourami
  • SAE
  • 10 x congo tetras
  • 4 x scissortail rasboras
  • approx 16 x harlequin rasboras
  • 10 x whitefin bentosi tetras
  • 4 x Cory sterbai
  • 1 x Stiphodon ornatus (who I have owned for over a decade despite my abuse. I am convinced this fish is immortal)
  • 6 x Otocinclus
  • 3 x amano shrimp
  • 3 x ember tetras
  • 5 x cherry barbs
  • plus one or two other small oddballs I have probably forgotten

Plants - I have been through quite a few and have kept those which have worked well. Most species are now a lot more successful with the added CO2.
Currently .......
Alternanthera reineckii rosaefolia (I am struggling a lot with this. Its growing but all leaves becoming algae covered after a couple of weeks)
Bacopa amplexicaulis Aquafleur (seems to need lower light so is tucked away at each end of the tank)
Cryptocoryne balansae (new)
Cryptocoryne Wendtii Red (new)
Eriocaulon sp vietnam (new)
Hygrophila corymbosa (new)
Hygrophila polysperma Rosanervig (new)
Limnophila heterophylla (continues to grow around 12" a week, to be phased out)
Limnophila rugosa (new)
Ludwigia palustris “super red”
Pogostemon helferi (this was an in vitro plant but has grown superbly for me so far. I have even had to remove a load)
Pogostemon samsonii (new)
Rotala bossii
Rotala colorata (thrives in this tank)
Rotala rotundifolia red (thrives but not enough light for good colouration)
Staurogene repens

Challenges with the tank have been mainly trying to deal with lighting the 24" depth and also substrate fertilisation.

Lighting - I have two cheap long Hygger luminaires across the top of the tank, so I have good coverage across the tank but the difference in PAR from top to bottom of the tank is huge. I have struggled to provide enough light on the substrate and at the same time control algae. CUrrently I am using a low-medium light strategy which seems to be successful with a lot of plants and algae is under reasonable control. Careful plant placement seems like could be key here. Lights are currently at around 70% so I do have room for increasing once I get CO2 and fertilisation properly sorted.
Substrate nutrients - I started off using API root tabs, which seemed to work OK but were very expensive to maintain on this size of tank. Then moved onto dried homemade clay balls rolled with dry fert salts. The clay particles have proved problematic as once disturbed into the water column they are so tiny they are hard for my filters to filter them out. I am still suffering from some water cloudiness from residual clay. I have now moved onto "injecting" aquatic pond compost under plants where I see necessary using an adapted 10ml syringe. This technique has worked well but the effects on plant growth are yet to be fully assessed as this is fairly new. Its certainly not a problem to water clarity of any is disturbed from the substrate. I have high hopes for this method of providing a decent amount of slow release nutrients in the substrate.

Ultimate goals - There is no specific aim of this tank in terms of aquascaping. It was always quite a loose idea of what I have trying to achieve. In my mind it is still 50% a "fish" tank and 50% a "planted" tank. I am balancing the needs of both. It does mean I add a lot of nutrients in terms of fish food and water column fertilisation has to be adapted accordingly. I have some hardscape, so it will not officially be a dutch aquascape. However, I feel that description is the nearest to my goal.
Being a bit of a shrimp nut I would love to have a load of dwarf shrimp in the tank but with the acara (who is staying) that is impossible. I am pleased to have recently discovered that he will tolerate large amano shrimp !
I think currently its mainly a question of discovering which plant species are really going to work well in the tank and then just letting them grow in.
Heres a couple more slightly closer pics.
071025a.webp
071025b.webp
IMG_6769_edited-1.webp
IMG_6784.webp
 

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