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Hey Everyone,

Does Lemon juice work to reduce PH in a system?

I bought some rock wool to start some lettuce seeds and the back of the package said to use lemon juice to reduce the water ph to 5.5 to start the seeds. 

I figured this would work in my system as well, which has been consistently coming up with a PH of 8.2, so I squeezed a few lemons into the system and tested the PH the next day and I noticed that the PH went down to 8. So I squeezed a bunch more lemons in. I put about 12 lemons worth of juice into my barelponic system, about 55 gallons of water.

I think the answer to my question is no, because my I tested the levels today, and my PH is still at 8, and all my other levels are weak. I'm about 2 months into cycling my system. My amonia already spiked and was consistently reeding 0.25 ppm, now its at 0. My Nitrites were reading 5ppm now they are 2 ppm and my Nitrates which were at 40ppm are now at 0. Did I just kill all my bacteria? Is all this lemon juice bad for the fish? 

I only have 2 gold fish that have survived the cycling. Should I add more fish? Should I change the water and start again? I have a lot of new growth in my grow beds right now.  is the lemon juice bad for the plants?

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Are you saying that if you have high alkaline water then the reagent methods of detecting ph maybe wrong? Or are you saying you could have media that renders the reagent tests inadequate?


I'm going to answer what I think your first question was: If you have a high pH. or alkaline then it's harder to bring it down over time, because you have what a high pH. brings a system, high pH.
Jason Eaton said:

Are you saying that if you have high alkaline water then the reagent methods of detecting ph maybe wrong? Or are you saying you could have media that renders the reagent tests inadequate?


Good info there, Jeremy. Adam mentioned his plants weren't growing at all a few hours ago. Good point about testing the means of testing pH.  I have different results with pen, litmus, and reagents every time I compare them. I don't know which one is typically more accurate. But if his pH is over 8, then iron is the only deficiency he's having trouble with, and in my opinion and experience plants do way better in acidic water.

I have seen a few make blanket statements that nitrifying bacteria will lower pH, and hence there is never a need to add acid, but rather a buffer of shells or something to prevent the pH from plummeting. The last Friendly newsletter said something to that affect. Hogwash. I have had AP tanks for nearly two years now and never has my pH dropped below 7.5 without acid, with medias of lava, granite, hydroton, river gravel, or no media at all. I stock heavy and feed heavy, and my ammonia is 0, so nitrifying bactria are alive and well. I would say from my regular reading of this community that high pH is very very common, and low pH is very rare, so other factors must be at play. Perhaps the stagnant pockets you mentioned are to blame. I didn't know that anaerobic conditions contribute to an a pH rise. I'm definitely guilty of poor housekeeping, and most of my growbeds are overworked an probably full of solids.  So if I cleaned out my growbeds I could expect a lowering of pH?

Great, thanks for all this everyone. Thats really good to hear Jon, that you've seen a lot of others with high PH. I do have tons of algae growth, I have three aquatic plants I put in for shelter for the fish as well. My pump constantly gets clogged with algea and stops working for hours at a time until I discover it, so I probably have really low oxygen levels and I've been experimenting with dumping lots of compost tea into the grow bed and the weird critters that swim in the tea for food for the fish, so I probably have some anaerobic action going on. I'm gonna give it some vinegar and see what happens.

Also, I only have two strong goldfish in my 55 gallon tank. I should probably get more fish in there as well. Any ideas on getting some food fish fry? I went to my Chinatown in Oakland and talked to one of the fish vendors, they said a few babies wouldn't be worth it to sell me and they probably wouldn't survive the transport. I've resorted to cold calling fish farms in the area. I'd like to get some trout, Carp or catfish going if I could. BUt no luck yet, any ideas on getting fish?  

I sell fingerlings, Adam. And I ship them all over Cali. I have right now or will have in the next couple weeks; tilapia, bluegill, red ear sunfish, green sunfish, Sacramento perch, Sacramento blackfish, channel cats, triploid carp, and trout. Send me a note.

In much of the country the cause of high pH is going to be the source water.  HARD WATER!  If you have hard water and you have to top up with it all the time, then your top up water can easily keep you pH over 7.5.  Lets face it if your tap water is equivalent to liquid limestone, it will keep you pH high.  My choice is to collect as much rain water as I can to use for topping up my system and then hopefully I only need the well water when I need to add calcium carbonate to buffer my system anyway.  However for those who can't get enough rain water, an RO filter might be the next best choice.  Constant use of acid is not really the best choice because if you have liquid limestone as your water, constant use of acid to counteract the carbonates is simply going to add a lot of whatever the acid is into your system as well as liberating an overabundance of calcium and whatever else into the water.  I've experienced lock out of potassium because of having to much calcium in my water.

Rare, occasional use of acid to adjust pH down might be ok but I still recommend doing it in a separate container and letting the water stabilize before using it to top up the system.  I would recommend muratic acid (hydrochloric acid) before I would recommend sulfuric acid for regular use in pH adjustment.  Please always use appropriate safety precautions when handling acid.

Thanks, Jeremy

Does anyone know if General Hydroponics PH-down is safe to use to lower PH? I've heard that it is, but one of the ingredients is citric acid.

 citric acidI've heard Sylvia uses pH down, but don't buy it for aquaponics, citric acid isn't safe for bacteria.

Jason Rampollo said:

Does anyone know if General Hydroponics PH-down is safe to use to lower PH? I've heard that it is, but one of the ingredients is citric acid.

Thanks Eric.  My PH has been 7.6, but occasionally spikes up to 8 and rather quickly. My well water is hard so that may be why, but its seems to be high out of no where. I tested around noon and it was 7.6, tested again at 6pm and it was 8. Ive been cycling my new system with goldfish for about a week. I've been testing my ammonia level and it seems to be just above 0. Nitrite level is 0, no nitrates yet. I'm not too sure how to keep the PH down. I've been losing about 2-3 goldfish per day. I suppose because the PH keeps spiking up, but I'm not sure?

If your pH is low at dawn and high late in the day, and you have algae, the pH swings would be because of the algae.  See overnight the algae uses up dissolved oxygen and gives off CO2 which when mixed with water acts as a weak acid but then during the day the algae will use up CO2 and give off O2 there by raising the pH during the daylight hours.

Add more aeration and block all sun from the water till the algae clears and then only allow enough light in to let the fish know day from night.  Fish don't need sun tans.

I would not use the general hydroponic pH down that has more than one ingredient.  The one that has multiple ingredients will also add ammonia and if you already have fish you don't want that.  Phosphoric acid is the only hydroponic pH adjuster safe to use a pH down and I don't recommend any use of acid long term all the time.

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