how much hcl?

[alex281]

Well my system has been running great and all, however the growth is rather slow. im pretty sure the only thing thats really affecting growth that much would be the fact that my ph is around 8.3! i was thinking to run down to home depot and get some of the muriatic acid, but before i go, is this the best way for forcing a lower ph? how much would i actually need for a 50 gallon tank?

from what i read a lot of people seem to use hcl or just wait for it to go down. its already been a couple of months with no signs of dropping.also i used quickrete brand gravel and it says for use with ponds so i dont think its buffering the ph.

Thanks for the help!

[urbanfarmer]

It depends on the concentration of of the HCl you buy and how much water is in your system (at a minimum).

[davidstcldfl]

Alex, Just wondering....what is/was your water's PH 'before' you added it to the system, so we have a base starting point...?

I went to quickcrete's site....your right, it says you can use it in aquariums too. They have 3 kinds...allpurpose, deco pebbles and marble chips.
Quickcrete rocks are most likely limerock. If that is what you used, your PH will stay high for some time.
In a pond, a higher ph wouldn't be that big of a deal. Your more concerned with the fish, not the plant growth. In an aquarium, same thing, plus 'regular' water changes help keep the ph at a better level.
In aquaponics, the ph is a balance game between the plants and the fish.

I use a small bucket with a very small hole in the bottom. I fill it with system water, then add the acid to it. I let this slowly 'drip' into the system....some where after the water leaves the fish tank.
The acid I have is aprox 31%. It doesn't take much....I only add about a <1/4 of a cup at a time, to a system with 3000 gals.

'Less acid' is better....drop the ph VERY SLOWLY. Maybe like a 1/10 of a point each day.

[urbanfarmer]

pH swings not a big deal in my opinion, the pH swings as much as a point or two during a given 24-hour period, the sensitivity to pH depends on the fish

http://www.jstor.org/pss/4608069 (goldfish don't seem to care if the pH swings 4 points in a day)

http://www.pir.sa.gov.au/__data/assets/ ... atqual.pdf

pH levels
The pH is the measure of the hydrogen ion (H+) concentration in soil or water. The pH scale
ranges from 0 to 14 with a pH of 7 being neutral. A pH below 7 is acidic and an pH of above 7
is basic. An optimal pH range is between 6.5 and 9 however this will alter slightly depending on
the culture species.

pH will vary depending on a number of factors. Firstly pH levels of the pond water will change
depending on the aquatic life within the pond. Carbon dioxide produced by aquatic organisms
when they respire has an acidic reaction in the water. The pH in ponds will rise during the day
as phytoplankton and other aquatic plants remove CO2 from the water during photosynthesis.
The pH decreases at night because of respiration and production of CO2 by all organisms. The
fluctuation of pH levels will depend on algae levels within the pond (Fig 7).
Sub-optimal pH has a number of adverse affects on culture animals. It can cause stress,
increase susceptibility to disease, low production levels and poor growth. Signs of sub-optimal
pH include increase mucus on the gill surfaces of fish, damage to the eye lens, abnormal
swimming behaviour, fin fray, poor phytoplankton and zooplankton growth and can even cause
death.

In the case of freshwater crayfish low pH levels will cause the shell to become soft. This is due
to the shell of the crayfish being composed of calcium carbonate which reacts with acid.
Sub-optimal pH levels are usually caused by acidic water and soils, poorly buffered water (will
be discussed further on) and increased CO2 production.

Treatment methods will depend on whether there is a high pH problem or a low pH problem. To
treat a pond with low pH, a pond can be limed with agricultural limestone or fertilised to promote
plant growth. To decrease a high pH, the pond can be flushed with fresh water, feeding rates
can be reduced to decrease nutrient input into the pond, gypsum (CaSO4) can be added to
increase the calcium concentration, or alum (AlSO4) can be added in extreme cases.

The above article might make you think, "there's no algae in my system". I assure you there is, but there's also something else that undergoes photosynthesis and respiration cycles... your plants... yes, at night.

That's just my 2 cents!



1 9 0 0 ! ! !

[davidstcldfl]

pH swings not a big deal in my opinion, the pH swings as much as a point or two during a given 24-hour period, the sensitivity to pH depends on the fish

Even using my 'bucket application'....the water's ph is changing in a 'few hours' at best. In alex's small system, maybe a 100 gallons or so, it won't even be that long.

I'd rather encourage someone to 'error' on the side of caution, then to do the guy thing...'more is better'.
I tried the latter of the two and I managed to teach my fish to 'roll on their sides' the 1st time I used muriatic acid....and yes, they were healthy goldfish.
I was fortunate I was there....I quickly added other water to the fish tank.

[urbanfarmer]

True. I agree to err on the side of caution, especially with newcomers.

I was just pointing out that IF we used the "right amount"of HCl it would be fine to dump it all in because pH swings of 1-2 points are an everyday occurrence in AP systems.

HCl will not only change the pH but increase the chlorine concentration in the water. The chlorine is more likely going to kill something like goldfish than Tilapia (depending how much you add it will kill anything though). However, the "right" amount will add a very small amount of chlorine, but it will change the pH by 1-2 points.

I'm sure the picture to the left of my post is scaring you, but I assure you, I am a highly trained madman with chemicals.

[davidstcldfl]

HCl will not only change the pH but increase the chlorine concentration in the water.

UF,can you clarify this statement for me ?
His water is several months old, and most likely he's already treated for chlorine/chloromines, so there is no chlorine to be 'concentrated'..... Or, is the acid adding chlorine ?

Tossing UF under the Lynx. That's the bus system in Orlando... Alex's tank is 50 gals, lets say he has an aprox 1:1 ratio..or 100 gallons of water....so how much, 31% muratic acid, can he add to drop his PH 1 point ?
Remember, this change will happen in a few minutes....not in the 24 hour, natural ph swing, you previously mentioned.

[urbanfarmer]

HCl will not only change the pH but increase the chlorine concentration in the water.

UF,can you clarify this statement for me ?
His water is several months old, and most likely he's already treated for chlorine/chloromines, so there is no chlorine to be 'concentrated'..... Or, is the acid adding chlorine ?

Tossing UF under the Lynx. That's the bus system in Orlando... Alex's tank is 50 gals, lets say he has an aprox 1:1 ratio..or 100 gallons of water....so how much, 31% muratic acid, can he add to drop his PH 1 point ?
Remember, this change will happen in a few minutes....not in the 24 hour, natural ph swing, you previously mentioned.

The pH change is "instant" except for the fact the water needs to be mixed. You can have spots in the water where the pH is 2, 3, 4, etc. The reactions are far more complex than outlined below. Everything from buffering agents to organic matter to living microbes and other organisms that interact with the chemical will change the final value. I have no way to calculate this.

-----------------------------------------

HCl is one part hydrogen atom and one part chlorine atom. When it disassociates in the water it releases these ions in the water, free to react once more.

-----------------------------------------

We want the concentration at 0.0000001 M H+ in his 100 gallons of water. That's 378 liters. i'm using the density of 32% HCl because that's what I have handy without doing more calculations and I'm feeling quite lazy right now. 10.17 mol/dm^3 in the 32% HCl. To simplify things we will assume it's magical water that has no pH and we are adding the hydrogen ions (the ions from the 8.2 pH is insignificant for our purposes anyway).

moles of hydrogen ions needed:
(378 L) x (0.0000001 M H+) = 0.0000378 mol of H+

volume of 32% HCl (muriatic acid) needed:
(0.0000378 mol of H+) x (1 dm^3 / 10.17 mol) = 0.000003716814159292 dm^3 = 0.003716814159292 mL = 0.004 mL of 32% HCl

This assumes no buffers in the water. If limestone has been reacting with the water, there will likely be an insane amount of a buffering agent in the solution, which translates into more acid than stated above (that is about 1/10 of a drop by the way, which is such a small amount it would be hard to measure).

What I have done in the past with LARGER systems is calculate the above and add THAT MUCH TO START. Basically, I know adding that much will NOT change it any LOWER than anticipated; therefore, it is a safe amount to add into a system all at once. I have done this with 91% HCl, which by the way is very dangerous and I don't recommend anyone play with the stuff without a full chemical body suit!

BTW, it would take 1 L added to 1000 L of water to get the chlorine concentration to about what normal tap water is in the USA (3-4 ppm). It would also make the pH of the water 3 (better understood as 1,000,00% the pH of a 7 pH solution).

[alex281]

as far as capacity there should be a minimum of 50 gallons. however im finding that i have to fill up my homedepot bucket and add it weekly so im not sure about the chlorine levels. the bucket idea seems like a great way to add. ill let you know the concentration of the acid when i get it.

Thanks for the answers! seriously helpful!

[davidstcldfl]

At UF: if we had a smile face with a 'thumbs up', I'd post it here for you..

At Alex: so your adding about 10% more water to the system 'each week'. That may account for your slow growth.....besides a high PH, you may be losing lots of nutes due to a possible leak (?)


The water your adding...
'what' is it's PH ?

If your not pre-treating the added water for chlorine/chloromines....plus you start adding acid....remeber what UF shared, you'll have even more chlorine