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ways to get more co2 in my tank

D

dernon

Seedling
Joined
10 Oct 2015
Messages
5
Hi everyone,finally joined up after lurking here for a long while. I have a 6 foot soil tank set up for nearly 2 years now,its my first attempt at plants,and I must say at the beginning it seemed simple,plants grew great,very little algae all good. But slowly things started to change,growth slowed,algae appeared etc. So I lowered lights added some ferts and although its still ok its nothing like it was a year ago especially the stem plants. It was only recently while listening to an interview with Diana Walstad I realised it was co2 related. She decribed my experience exactly and said that after about a year most of the organic material is broken down and therefore the Co2 given off becomes less and less. So what to do ?? I had a couple of ideas and I have decided to ask you good people if they have any merit or have been tried before.
firstly add a lot of floating plants and emersed plants,the idea being they get co2 from the air,but more importantly through respiration of the roots would release co2 into the water for the other plants to use. Have I this correct ? Would it make any difference ? Has it been tried or proven to work ? I have seen floaters recommended for reducing light but could they also add co2??
The other idea was ,as I am probably over filtering my tank anyway,to add some organic material to the filter to be broken down by bacteria thereby releasing co2. This would need to be though and my cause more problems than it solves.
Anyway ,anyone have any thoughts on these??. Please be gentle,its my first post and I have very little scientific knowledge. Maybe they are ridiculous ideas.....
 
Welcome Dernon. I dont believe adding floater will increase the co2 in your tank at all. Youve got a few options though:
1) If plants are the easy type then you can up your surface ripple in order to keep the supply of co2 stable from the atmosphere. This way plants never run out of it, even though levels will be low. In a low tech tank its recommended nowadays to keep surface movement at all times. Its better in the long run. But the catch is you cant keep some species and growth will be slow. If you can even a venturi will help your plants a lot.
2) liquid carbon. This is your next best option. But it might kill some plants like Vallisneria or Egeria.
3) Gas CO2. Dont recommend this. Its not as simple as just adding co2.

Also remember to always dose nutrients.
 
I believe a lot of your problems can come from increased plantmass too. The required amounts of ferts end CO2 for growth increase with increased plantmass, thus pushing you in the "to little available" category.
Adding floaters will lessen the growth through decreased light in the submerged plants, the decreasing demand. So this might help.
Adding a surface movement through 1) the filter outlet or 2) an airstone will increase CO2 levels in the tank. Just slightly, but it maybe enough.
Decreasing the lighting period me decrease the demands too.
Adding organic material is a dangerous way, because you don´t add pure CO2 but a lot of compounds which have riscs (thats why in a soil tank it is capped away from the water under the gravel).
If you want to add CO2 you might want to have a look at bio CO2 (Sugar and yeast).but it shouldn't be neccesary for a low tech setup.
 
Hi,thank you all for taking the time to read my post. I suppose I was just trying to come up with an idea without injecting co2,and wondered if anyone had tried anything different. I'm sure you are correct Jose in that floaters wouldn't add any co2. I know roots do add some by respiration but it is probably not a lot. And yes edvet adding something to the filter would be very risky and potentially do more damage than good. Thanks again for your advice
 
Do you have any picture of the tank? Can you show what the plants look like exactly so we can get an idea of symptoms.
I understand the substrate is soil. What have you capped the soil with?
Over a year that soil will be saturated with more organics. The organics don't run out unfortunately. Hence people siphon their substrates to reduce them.
I've got two soil tanks, one is running for 3 years, one for 2 years and I am yet to experience the "CO2" problem you've got with your tank. I've had all sort of nutrient deficiencies though and I dose ferts.
The biggest and first issue is potassium, then nitrogen, then possibly some micro deficiencies here and there. Have you dosed anything at all so far?
The problem with organics and CO2 is that you need oxygen for aerobic decomposition. Only aerobic decomposition releases CO2. Anaerobic decomposition(when the substrate is too deep) releases hydrogen sulphide, methane and other similar toxic gasses. When that happens, it starts killing the plants too. So then you'll have very little co2 production and withering plants. Especially if there's little surface agitation to compensate for oxygen.

Diana Walstad is correct that CO2 production may slow down. But it will not slow down to the point of having major problems with your plants, just slower but steady growth. I've got away without algae for that period of time so surely everyone can if following the same principle.
 
Hi,thanks for the detailed response. I'll try to get a few pics up. Its an inch of ji no 3 capped with gravel. I add about 50/75ml of micro and macro each week after 20% water change.its about 550l tank. To be fair its not a disaster,crypts are spreading rapidly and i have to remove plantlets every couple of weeks to keep them in check. Dwarf sag doing ok and a couple of tiger lotus doing fine as is hygro. Coryembosa,forgive the spelling. Java fern also doing well. However a few others bacopa caroliniana and monneri and particularly wisteria aren't going so well. The wisteria grew like a weed for ages but now shows very little new growth. I also have bba on the crypts and some on java fern and sag. I will try to get a few pics i know they are worth a thousand words
 
Following with interest as your tank seems similar to the one I have planned... Can I ask how you know it's a CO2 deficiency and not something else?


Sent from my iPhone using Tapatalk
 
Hi Chris,i don't know for sure that its co2 related. Growth of some of the stem plants has slowed significantly in the last few months and while listening to an interview on youtube with Diana Walstad she said that it was normal after a year or so for stem plants to struggle because most of the organic material in the soil has been broken down and it gives off a lot less co2 and that some plants cant compete for co2 with the hardier crypts, swords java fern etc.I have no idea how true that statement is,only what she put it down to . I also have lowered the lights to try to keep algae at bay and maybe this could be part of the problem. To be honest i might just change the ones which aren't doing well and replace them with different species and see how they go.
 
Interestingly Crypts, sword, vallis, and a few others almost always do well. Did you know they can use bicarbonates from the water as a carbon source?. If you only use carbonate loving species you dont even need to supply co2.
 
Hi,thank you jose for the info,yes i am aware that some plants can use bicarbonates although most of the science goes way over my head. Thank you for the links edvet. Thank you troi ,i will try to get some pics up as soon as i figure out how to do it on my phone. There isn't too much wrong with the tank really,some algae on some of the plants,its just it looked a lot healthier a year ago . I am using a diy set of leds. They are cree xte on 1000ma drivers so as far as i can make out about 300 lumens for the 28 cool white and around 240 for the 14 warm white so 11760 lumens in total over 550l tank. I worked out these figures from the cree data sheet using the graphs so its my best estimate ,if anyone has better info please let me know. I also have no idea of the par readings. They are also on a pwm controller and i had them at over 90% for the first 6 months or more but gradually had to reduce them to keep algae at bay,currently they are around 35% . Although I am delighted with the lights as they are so easy to control,trying to get info on them is difficult compared to a shop bought unit unless you have access to a par meter i suppose,and i dont
 
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