Cycling new micro-system and pH

[mbmixon]

I am less than a week in on my first go at aquaponics after roughly three months of reading and research. This is a micro system by aquaponic standards; I selected this size to utilize hardware and resources we already had in an effort to learn about aquaponics on the cheap (relatively speaking). I am using a 30 gallon FT with two 15 gallon GB roughly 14'' wide x 23'' long x 12'' deep.

All connections were made, pump capabilities confirmed and plumbing tested prior to live start up. I have chosen to cycle with fish (40 feeder goldfish) and utilized a 4'' x 8'' dirty skimmer filter from the pet store to expedite the process. Stocking density is quite high and I plan to deal with this as needed (was expecting a mortality rate higher than zero!!!).

As of today my system pH has dropped to 7.0 from 7.6 which I believe is to be expected during cycling (ammonia is 0-0.25 ppm, nitrite is 0.25ppm and nitrate is 10ppm). I have added a few seedlings of romaine and leaf lettuce to the GBs. I am utilizing a Aerogarden with starter tray and plugs as a raft starter.

My question is regarding the pH and subsequent water adds due to evaporation, etc. My tap water has a pH of 8.0 and I am currently keeping a gallon pitcher on hand for adds, allowing sufficient time for off gassing of chlorine.
Should I try to adjust the pH in my add pitcher to target 7.0 or should I continue with the higher pH adds (perhaps a half gallon at a time) and allow the system to work out the pH? Also, is there a formula to determine the pH of a known sample after adding a known quantity at a different pH.

Thank you for any advice and apologies if this was posted in the wrong area.
Michael

[topz]

Welcome to the forums! Great questions. Half a gallon in 30 gallons is probably not going to mess anything up as your system will work to lower the ph naturally. What media have you got in your gbs?

[mbmixon]

I am using hydroton for the grow media. I must say that the time involved in cleaning the hydroton was not covered adequately in the books and documents that I researched. My children saved me a good bit of time by helping and seemed to enjoy that part of the project; playing in the garden hose anyway! I have larger scale plans for the next system and will need to come up with a quicker method for rinsing a large quantity. I am actually considering expanded shale as there is a supplier not too far away and I really like the cost and weight benefits.

[topz]

Oh the joy of cleaning the dust and debris from media before getting it dirty. Glad I don't have to do anymore this year.

[mbmixon]

Well the pH continues to drop. This morning is has dropped below 6.4 and two fish have died. Looks like the system may need a little bump and buffer.

I plan to pick up some potassium bicarbonate today, as my local hydroponics store is also a home brew store. Are they any other suggestions for gently raising pH to avoid a massive spike?

I knew when designing this micro-system that big swings were likely; would have preferred to start with a 200 plus gallon tank, but it wasn't possible from a budgetary perspective.

[topz]

Egg shells. They will raise the ph slowly and buffer the solution against and rapid drops. Just becareful adjusting things too often or too much is not suggested. As for the loss of fish your going get that while cycling with fish. Goldfish are going to grow big in a hurry so a few here and there won't be the end of the world. Don't adjust the ph faster then .2 or .3 up or down or you run the risk of killing a good chunk of the remaining fish. Enough doom and gloom. Let us know what you decide and what happens.

[Apollo]

Sorry to hear about you 2 fish.

Egg shells will buffer your pH back up, boil the shells and place them in a flow though bag. Put bag where your water returns back from your GB to speed up the process, Remove bag once your pH reaches your desired level, some say it can remain in your FT and will only buffer pH as high as 7.2

[mbmixon]

We have chickens so I have a ready supply of egg shells. I'll give it a shot and report back.
Thanks for the feedback!
Michael

[mbmixon]

Just a quick follow up on the egg shell addition. Things have stabilized with the pH, though still a bit low in the 6.2 - 6.4 range. The fish are doing better as well. I had one of the grow bed return tubes flowing over the bag, but realized in doing so I was cutting the tank aeration by between a quarter and a third. Moved the bag close to the return flow but not directly under so that returning water would continue to provide aeration.

Side note: After boiling the egg shells, I ground them up in a "bullet" blender before putting them in the bag and into the tank. There was an initial clouding (slight) but that cleared up after the first flood cycle.

Thanks for the information and hopefully as the system cycles the pH will climb slowly into the 6.8 - 7.0 range.

[mbmixon]

Another update:
Still unable to raise pH to desired range of 6.8 to 7.0. pH is holding between 6.0 and 6.4 even after water changes which bring the pH up to 6.8. Within a day or two the pH returns to the low range.
I added the rest of the eggshells that I had ground and haven't seen a change to the positive, though I cannot altogether discount their importance as they may be preventing the pH from dropping below 6.0.
Ammonium has remained consistently high (2.0-4.0 ppm) but the feeder goldfish are doing OK (which is why I chose to start with goldfish). There has been no change in the nitrite or nitrate levels for weeks; it remains at 0ppm. I believe the low pH is affecting the nitrosomonas/nitrospira bacteria negatively.
I don't want to get into chemical adds, but I suppose it is time to consider pH up for Hydroponics/Aquaponics. Has anyone had success maintaining their system with this product. I understand that the product designed for aquarium use adds significant salts and can wreck a AP system.